Insurer Admits Bad Accounting in Several Deals
American International Group acknowledges that its accounting for number of transactions, including deal with unit of Warren E Buffett's Berkshire Hathaway, was improper, and that impact of accounting errors would lower its book value by $1.7 billion; this is AIG's fullest disclosure since questions about its dealings first emerged last year; federal and state regulators are digging through dozens of transactions to determine how extensively it dressed up its financial condition; investigators are focusing on 2000 transaction between AIG and General Re unit of Berkshire Hathaway that artificially inflated AIG's reserves by $500 million; latest disclosure may not bode well for Maurice R Greenberg, who was forced to step down as chief executive after regulators uncovered evidence that he initiated transaction with General Re; his liability will reportedly rest on what he understood about transfer of risk in General Re deal and whether he believed transaction to be questionable; company also cites flawed accounting of its business with reinsurers that it controls in Bermuda and Barbados (M)