As the annual meeting of Berkshire Hathaway kicks off this weekend under ominous, stormy skies, a particular cloud may be hanging over chairman Warren Buffett himself after allegations surfaced Friday that two of his companies may violate corporate ethics rules.

The Connecticut attorney general, Richard Blumenthal, said he was investigating a possible conflict of interest arising from Berkshire's nearly 20 percent stake in credit-rating agency Moody's and the Berkshire Hathaway Assurance Corp., a new municipal-bond insurer controlled by Buffett's $200 billion conglomerate, which receives credit ratings from Moody's.

Blumenthal is probing what he described to Bloomberg News as a "clear and direct conflict of interest for Moody's to rate a company owned by such a significant Moody's shareholder." A favorable credit rating for the Berkshire municipal-bond unit could give it a leg up against competitors M.B.I.A. and Ambac.

Buffett is expected to address the Moody's issue for the first time at Saturday's marathon five-hour question-and-answer session with shareholders.

Tony Mirenda, a spokesman for Moody's, played down the probe, saying the rating agency has "a long-standing policy of not discussing our ratings with shareholders and nonemployee members of the board of directors." Berkshire, he said, is "a passive investor that has never contacted us regarding our ratings."

For the Buffett faithful—the majority of the 30,000 people expected to attend the "Woodstock of Capitalism"—the "Oracle of Omaha" remains above reproach.

"It will be just like the Gen Re thing, which Buffett handled very well," said Berkshire investor Ashley Goul, the president of a sportswear embroidery company in Boise, Idaho, over coffee at Scooter's Coffeehouse in downtown Omaha.

A federal investigation of General Re, the Berkshire-owned reinsurer that was implicated in sham transactions with A.I.G., the insurance giant, led to criminal fraud convictions of four former General Re executives. Last month, Joseph Brandon, the chairman and C.E.O. of General Re and a Buffett favorite, resigned from the company under pressure from federal prosecutors.

"I'm very confident that everything has been done above board, and if mistakes were made, I'm certain they will be corrected," Goul said.