April 11, 1983

A projected meeting of Latin American nations to discuss the widening conflict in Central America has been postponed indefinitely, according to diplomats here. Instead, the diplomats indicated that a new initiative would be proposed soon by four of the region's governments. The meeting on Central America, which had been expected to take place this month in the Dominican Republic, would have included representatives of five Central American nations - Costa Rica, Honduras, El Salvador, Guatemala and Nicaragua - as well as observers from Panama, Mexico, Venezuela, Colombia and the Dominican Republic. The Latin American nations had planned to exclude the United States from the talks, a move to which the Reagan Administration did not object.

Thomson McKinnon Inc., though among the nation's 20 largest brokerage concerns, makes little noise on Wall Street. Competitors and analysts most often describe the company as reserved and conservative - ''the traditional wire house,'' said one. John J. Maloney Jr., the company's chairman and chief executive officer, puts little weight in such observations. ''Anyone who says that doesn't know much about Thomson McKinnon,'' he said Friday Last week, Thomson announced its intention to enter the banking business. If Federal regulators approve, it will acquire the First Federal Savings and Loan Association, a small thrift institution in Madison, Conn., in a cash transaction valued at $10.8 million. The deal would result in the first purchase of a savings institution by a brokerage firm.

An article in Postings in yesterday's Real Estate section misstated the starting time of a conference tomorrow on back-office space in New York City. The conference begins at 6 P.M.

Vietnamese soldiers herded Cambodian civilians into bunkers last week and threw hand grenades at them, according to Cambodians who said they had been victims or witnesses of such attacks. These statements, made in interviews today by 13 Cambodian civilians at a Red Cross hospital near this border town, were the first accounts supporting recent charges by a Cambodian insurgent leader that Vietnamese troops had deliberately attacked civilians in their drive against rebel forces near the Thai-Cambodian frontier. The civilians said the grenade attacks took place over three days, beginning April 3, at O Smach, a camp on the Cambodian side of the border. That was the day the Vietnamese fought their way into the camp; they completed its capture on April 4. No Figures on the Dead Those interviewed did not give figures on the total number of civilians killed but said most of the victims they knew about had survived. The insurgent leader said last week that ''several hundreds'' had been killed.

With only five days remaining before the deadline for filing Federal personal income tax returns, financial institutions in New York City and around the country are reporting a last-minute surge in depositors opening Individual Retirement Accounts to qualify for a deduction on 1982 taxes. ''They've really been coming in in waves, especially since April 1,'' said Cynthia Bailey of the Chase Manhattan Bank. Some other I.R.A.-sponsoring institutions have been reporting averages of 5,000 to 7,000 new accounts a day in recent weeks, as savers seek to beat the April 15 tax deadline. The institutions are encouraging this rush to open the retirement accounts in nationwide promotional campaigns. Big newspaper display advertisements and spots on radio and television are touting the investment and tax opportunities offered by I.R.A.'s.