UPDATE, 8:10 PM: Reached late Thursday, Rosenthal said “Joel and I always had a great collaboration and we remain close friends. And Joel was instrumental in negotiating for Keith Olbermann to come to Current.”

PREVIOUS, 4:15 PM: Mark Rosenthal decided to leave because Joel Hyatt was crowding him in, we’re told. The co-founder wanted to run Current again after Rosenthal recruited Keith Olbermann to come on board. The channel began to generate a lot of buzz as its focus shifted to news commentary and politics as opposed to long form non-fiction programming. Hyatt’s desire to run the operation reached the point where he and Rosenthal agreed a few months ago to be co-CEOs, although the company didn’t announce that change. But the the channel’s too small to require two chiefs. What’s more, Rosenthal had held bigger jobs by himself when he was CEO of Interpublic Media and COO of MTV Networks. He was a board member at Current when Hyatt asked him to step in and professionalize the programming, marketing, affiliate sales, ad sales, and research efforts at the channel that used to be based in San Francisco. Olbermann’s said to be upset by Rosenthal’s decision to leave his job and the Current board. But even Current’s most famous personality doesn’t have the clout to overrule Hyatt.

PREVIOUS, 3:03 PM: Current TV has just released this statement about its CEO Mark Rosenthal leaving the network, a little more than a month after the premiere of the revamping network’s new flagship news show Countdown With Keith Olbermann. Co-founder Joel Hyatt is replacing him. The statement:

After six years as a board member, and two years leading Current as CEO, Mark Rosenthal is leaving the company and Joel Hyatt, who co-founded Current with Chairman Al Gore, will again assume the title of CEO. During Mark’s tenure, Current has become a focused cable network with a world class leadership team, a new brand identity, a move towards long-form, ratings-driven factual programming and a solid foundation for growth. These results helped pave the way for Current’s recently successful launch of Countdown With Keith Olbermann and the network’s major strategic shift to become a political commentary and news analysis network, with a clear, progressive point of view.