The rumor mill kicked into high gear this morning when Valleywag posted a story saying Ustream was in advanced negotiations to be acquired by Microsoft for $50 million. Quick calls to Ustream CEO Chuck Wallace and a Microsoft rep got us the standard “We don’t comment on rumors.”

According to Wallace, the company is in the midst of raising its Series A round of financing, though he wouldn’t say how much Ustream is looking to raise (the company pulled in over $2 million in previous angel rounds).

When asked if Ustream was open to being acquired, Wallace responded with, “We are focusing on Series A. If people want to talk with us about acquisitions, we’re open to that.”

Ustream now has 170,000 registered broadcasters, and during the month of January delivered over 1.5 million viewer hours of content.

But the company though is shifting focus away from lifecasting and onto eventcasting. “We are certainly focused on the eventcasting,” said Wallace. “We have a great platform and we welcome everybody, but our focus is certainly on these deeper events.”

Judging from our call, Wallace will be focused today on not commenting on a possible acquisition.