So much for a new boss ending Yahoo's drama. Why did the company's chairman meet Microsoft's Steve Ballmer at the Time Warner Center Thursday, two days after Yahoo named Carol Bartz its new CEO?

A tipster reports spotting the two:

On my way down the elevator, I was stopped on the 5th floor and in walk Roy Bostock and Steve Ballmer. Kind hellos were exchanged. As we entered the lobby they both walked out and seemingly proceeded to lunch together.

An odd couple. Bostock, an adman who now runs Yahoo's board of directors, and Ballmer, the shouty head of the software giant, have spent most of the past year badmouthing each other after a merger deal worth $45 billion fell apart. (Microsoft badly wanted Yahoo's search business, so it could better compete with Google; but Yahoo wanted more money and less uncertainty, since any merger might take a year to get past regulators.)

At one point, a Microsoft flack called Yahoo's recounting of how the deal went down as "revisionist history." Bostock, meanwhile, testily defended himself at Yahoo's last shareholder meeting. And now they're back together, smiling and lunching?

The first conclusion one might jump to: Bostock, having filled Yahoo's CEO chair with a seatwarmer, is ready to cut a deal with Microsoft. Ballmer has already said he'd like to negotiate a deal with Yahoo, and soon. But why would Bartz, a hardcharging, tough-talking sort who formerly served as design-software maker Autodesk's longtime CEO, take the job if she was just going to see the company sold?

A more innocent possibility: Bostock and Ballmer may have agreed to talk as soon as Yahoo appointed a new CEO, and they happened to both be in New York at the same time.

A more disturbing scenario: Bostock is trying to negotiate a sale of the company or its search business behind Bartz's back. A clumsy move, but Bostock, whom many Yahoos regard as an ineffectual "empty suit," might just be stupid enough to try it — in which case Bartz will have to spend her first months battling a rogue board chairman rather than fixing Yahoo's urgent problems. She would do well to oust Bostock, at any rate; as grateful as she might be for the job, Bostock has been a disastrous chairman for Yahoo, from his mishandling of the Microsoft negotiations to his foolish appointment of Yahoo founder Jerry Yang as CEO.

And there's one last twist: The place where they met. Time Warner has long been interested in unloading AOL, its troubled Internet unit, on Yahoo — but only at the right price. And Microsoft might still want to strike a search deal with a combined AOL-Yahoo. Was the popular midtown-Manhattan location just coincidence — or were Bostock and Ballmer also paying visits to AOL's parent? Tips are welcome.