What was going on when I was born?

The movie ''Krush Groove'' is a somewhat slapstick comedy filled with song and dance and containing little violence, yet on several occasions violent incidents have broken out following a showing. The most recent of those incidents occurred last weekend in this Nassau County community not far from the Queens border. The police say that as many as 225 teen-agers may have been involved in the fighting. ''Krush Groove,'' which is about black teen-agers in New York City who start out washing cars and end up signing recording contracts, has been drawing a predominantly black audience, according to theater owners. The clashes on Long Island appeared to be between them and the largely white audiences attending other films at adjoining theaters.

To American intelligence officials, Vitaly Yurchenko's defection had seemed an extraordinary coup, a signal that the tide in the ideological war was turning in favor of the United States. Just last week, officials were calling Mr. Yurchenko a new breed of defector who left because he was disillusioned with Communism, not because he was in trouble or in debt. Before his redefection, a White House official, speaking of Mr. Yurchenko and other recent defectors, said, ''It certainly has caught the attention of senior people in Government, the difference between these cases and the ones of the past.'' But today, officials at the Central Intelligence Agency said they were stunned and perplexed.

Gencorp Inc., which was once known as the General Tire and Rubber Company, said yesterday that it would ask its board to authorize the buyback of ''a significant'' portion of its stock, using some $700 million in pretax proceeds, principally from the sale of two television stations. RKO General Inc., a division of Gencorp, has agreed to sell KHJ-TV, a Los Angeles independent television station, to the Westinghouse Electric Corporation for $310 million, Gencorp said. RKO is also exploring the sale of WOR-TV, the New Jersey-based station that covers the New York market. That station, which Westinghouse is also interested in buying, could sell for $300 million to $400 million. The company has additional funds coming from its agreement last month to sell its stake in Frontier Holdings Inc., an airline holding company, to People Express for $300 million.

DURING their years in the service, some had not yet come to realize they were homosexuals. Others were aware of it but kept the matter to themselves or confided in the few others in the same situation. To acknowledge it, they knew, could abruptly end their military careers. Now 10, 20 or even 50 years after they were mustered out, much has changed for many of America's homosexual veterans. They not only want to acknowledge their sexual orientation publicly but to proclaim their patriotism at the same time -by marching down Fifth Avenue, under the banner of the Gay Veterans Association, in the annual Veterans Day parade.

In perverse moments, Herbert M. Sandler almost wishes interest rates would rise. That is an extraordinary musing for a thrift unit officer such as Mr. Sandler, chairman of the Golden West Financial Corporation, a $12 billion savings and loan institution based in Oakland, Calif. Higher interest rates would raise the price that thrift units pay for money at a time when hundreds of them around the country are already fighting for survival. But Mr. Sandler would not mind showing ''how far we've come.'' That is because, while the public perception is that the industry is on the ropes, many thrift units, including Golden West Financial, are earning record sums this year, and are also restructuring their balance sheets to reduce their vulnerability to a new round of higher interest rates.

The Senate today approved the nomination of Winston Lord as Ambassador to China after President Reagan intervened to end a five-week impasse caused by the opposition of Senator Jesse Helms. Mr. Lord, 48 years old, a former head of the Council on Foreign Relations and an associate of former Secretary of State Henry A. Kissinger, was approved by a vote of 87 to 7. The vote was taken after Mr. Helms, Republican of North Carolina, relinquished his hold on the nomination after a conversation with the President. Filibuster Was Threatened Mr. Helms had bottled up the nomination, exercising a traditional Senate prerogative , in an attempt to win assurances from the Administration that it would provide no assistance to current Chinese population control programs. Mr. Helms indicated he had received the assurances he sought from the President.

Sales of new American-made automobiles continued to slide in late October, with sales down 14.1 percent in the last 10 days of the month from the period a year ago, the manufacturers reported here today. In the Oct. 21-31 period, which had 10 selling days this year and nine in 1984, the daily selling rate was 23,364, compared with 27,184 last year. For all of October, domestic sales were off 13.2 percent from last year. There were 27 selling days in the months this year and last year. October's figures followed record deliveries during September, when low-cost financing incentives were being offered.

When James L. Emery was picked by President Reagan to run the United States portion of the St. Lawrence Seaway, he was told he would have to do something about the destructive competition among the Great Lakes ports. ''Before my confirmation, senators told me the first thing I would have to do is go out and unite these guys,'' Mr. Emery recalled. ''I told them they are united - they're all opposed to my nomination.'' It is an understatement to say that Mr. Emery, long a figure in Republican politics in New York State, was not warmly received when, in February 1984, he became the first New Yorker to be the administrator of the St. Lawrence Seaway Development Corporation.

Companies Gencorp will buy back ''a significant'' portion of its stock, using money from the sale of two television stations. The company's RKO General unit has agreed to sell KHJ-TV, a Los Angeles independent station, to Westinghouse for $310 million. It is also exploring the sale of WOR-TV, a New Jersey-based station that serves the New York market; that deal could bring in $300 million to $400 million. The moves were warmly received on Wall Street; Gencorp stock rose $7.125, to $61.375. [D1.] WOR-TV offers news, reruns and classic movies but gets its highest ratings from sports broadcasts. [D4.] Sales of American-made cars were down 14.1 percent in late October, compared with the 1984 period. Analysts said the weakness would not be overcome until financing incentives are restored. Sales of imported cars soared 24.8 percent, increasing their market share to 30.6 percent, their highest share since August 1982. [D1.]

International Vitaly Yurchenko has freely decided to return home to the Soviet Union, State Department officials said after a meeting with the K.G.B. official who had been described as a prized defector to the United States. Several officials said he had been disappointed by the collapse of a love affair with a woman in Canada and angered by a succession of news articles about him. [Page A1, Column 1.] To American intelligence officials, Vitaly Yurchenko's defection last summer seemed an extraordinary coup, a clear signal that the tide in the ideological war between East and West was turning in favor of the United States. But yesterday C.I.A. officials said they were stunned and perplexed. [A1:1-3.]

With the campaign behind him and an unquestioned mandate in hand, Governor Kean is set to start work on his next political agenda, one he hopes will carry him outside New Jersey as a spokesman for an open and more broadly based Republican Party. He said he hoped the size of his victory would give political credibility to his message - that if the party wants to expand its base of support nationwide, it must open itself up to blacks and ethnic minorities. The victory ''should mean that a Republican candidate willing to reach out to the black community and ask for their votes is able to get them, which contradicts an article of faith in the Republican Party,'' he said. 'Educational Renaissance' Tonight Mr. Kean's supporters celebrated at the Governor's campaign headquarters here at the Holiday Inn.

Xerox has managed to do what hardly any other American company has done: stop the Japanese advance into its market. And its executives even maintain that in some sectors they are recapturing lost ground. The turnaround comes only after the company gave up more than half of the market for plain paper copiers, which it created and virtually owned in the 1960's. Xerox, which long dictated to customers and ignored emerging competition, has rethought virtually every facet of its business - from its basic approach to developing and manufacturing products to how it schedules lunch hours for employees. In doing so, it has narrowed significantly the advantage that such Japanese companies as Canon, Sharp and Ricoh had enjoyed.