The Yahoo board will be meeting in Silicon Valley tomorrow to discuss a wide range of worrisome issues facing the troubled Internet giant.

Meanwhile, several sources said, even more private equity investors are weighing making major investments in the company, all pretty much aimed at ousting said directors.

So far, that has only been Third Point’s Daniel Loeb, whose massive hedge fund now owns 5.1 percent of Yahoo.

Loeb appears tomorrow at the high-profile Delivering Alpha investor conference in New York at 2 pm PT, where he is expected to take another swing at Yahoo’s board.

His next moves, sources said, could include buying up more shares to put the pressure on and also presenting his own alternate slate of directors, much as activist investor Carl Icahn did several years ago at Yahoo.

Translation: Forget AOL’s CrunchGate — this is big-boy corporate battling!

Add that to the pile on Yahoo’s board meeting agenda, along with some other critical issues that include: Outlining the criteria for any CEO candidate and a discussion of headhunting firms to hire; a review of strategic alternatives, including a presentation by its investment advisors, Allen & Co.; and how to stabilize the company and reassure its dusting-off-their-resumes employees.

Finding answers to these questions is going to be difficult enough, but the ever increasing pressure from outside investors is going to make it even harder.

Some definite tire-kickers reportedly looking at a bid include Providence Equity Partners, Silver Lake, Blackstone, Texas Pacific Group and even KKR.

While KKR has reportedly close ties with Yahoo Chairman Roy Bostock, he is now the main target for pretty much everyone else.

That includes Loeb, as well as other major Yahoo shareholders.

That’s no surprise: Bostock, who is also on the boards of Morgan Stanley and Delta Airlines, has presided over a series of gaffes at Yahoo since he became chairman in 2008 (he’s been on the board since 2003).

Those have included: Yahoo’s bungled effort to stave off a takeover by Microsoft several years ago; the too-long enthusiasm for CEO Carol Bartz, who was hired in early 2009 and fired last week; sitting unusually still as competitors such as Facebook, Google and more have out-innovated and outgrown Yahoo; and, of course, the falling knife of a stock, which has dropped precipitously since Bostock has been in charge of the board.

As Loeb wrote in a letter he sent to the company:

“It is time that certain members of this Board were held accountable for its past failures and their individual roles. Accordingly, we insist that Mr. Bostock, who championed Ms. Bartz’s hiring and led the charge against the Microsoft deal, promptly resign from the Board.”

Said another source with knowledge of the situation: “Under Roy’s leadership, this weak and bumbling board took too long to fire a clearly failing CEO and now has no plan, except throwing up their hands and hoping someone comes along.”

Here is one certainty: Someone is going to come along and it is not going to be pretty.

The executive turmoil at the very top of Yahoo continues, with the company poised to announce the resignations of three top execs, including U.S. head Hilary Schneider (pictured here), according to sources close to the situation.

The other execs also leaving, which Yahoo (YHOO) is planning on revealing Friday: U.S. Audience head David Ko and, as BoomTown previously reported, VP of Media Jimmy Pitaro.

While some at Yahoo are trying to spin it as an ouster, sources close to the situation said that Schneider–who presides over media and advertising sales at Yahoo–has wanted to leave the company for a while, but was convinced to stay on by CEO Carol Bartz.

Schneider will, in fact, stay at Yahoo while it searches for her replacement. Heidrick & Struggles had already been headhunting candidates for her job in recent weeks.

Why Ko, who works directly for Schneider, is leaving now is uncertain, although sources said a lot of product control over properties under him is being moved over to Chief Product Officer Blake Irving.

Irving was hired several months ago by Bartz, and he has brought in many former colleagues from Microsoft (MSFT) to top product jobs at the company. And he’s appeared to have won the latest corporate power play too.

This entire mess–and that’s precisely what it is–calls into question the tenure of Bartz, a tough-talking, cost-cutting exec who was brought in to clean up Yahoo after the maelstrom around the failed takeover attempt by Microsoft several years ago.

She replaced co-founder Jerry Yang and came in with guns blazing and styling herself as an agent of change.

Except not too much as changed–except for finally striking a search technology deal with Microsoft–as the exodus of talent from Yahoo increases, advertising revenue growth is anemic, innovation is stalled, metrics are weak and the stock remains moribund.

In addition, Bartz’s frequent shoot-from-the-hip remarks appear to have alienated a number of partners, most recently in Asia.

This week, according to sources, some board members had an emergency meeting at Yahoo’s Sunnyvale, Calif., HQ to try to figure out how to deal with the burgeoning management issue.

Some speculate that they will hire a second-in-command to Bartz, who might be able to take over for her when her contract is up in 18 months.

Yahoo declined to comment.

People familiar with the matter tell me that DeWolfe and News Corp., specifically new digital boss Jon Miller, are discussing a leadership change today. News Corp. (NWS) officials declined to comment. (News Corp. is the owner of Dow Jones, which owns this Web site.)

Sources tell me Miller hadn’t been planning on getting rid of DeWolfe (pictured above) in the near future, and that until yesterday he was still evaluating his options. News Corp. CEO Rupert Murdoch had once treated DeWolfe as a favorite and gave him significant autonomy at MySpace. But Murdoch, who brought Miller on earlier this month, has been leaning toward a change as MySpace’s traffic has stagnated and its buzz and momentum have moved to Facebook.

Still, Murdoch had left the decision about the site’s leadership to Miller, his new hire, sources said. One possibility: Elevating DeWolfe to a nonexecutive advisory position.

Those options narrowed last night once TechCrunch ran a story claiming that News Corp. had hired a headhunting firm to “scour for possible replacements” for DeWolfe.

News Corp. hadn’t actually hired a headhunter, I’m told by multiple sources. But I’m also told that the report was enough to spook DeWolfe into calling Miller to ask what his plans were. That conversation led to today’s negotiations, which will likely lead to his stepping down as CEO, although he may remain affiliated with MySpace in some capacity.

Meanwhile, News Corp. has been talking to Van Natta (pictured here) about taking DeWolfe’s place. Van Natta, who had been a highly regarded executive at Facebook, was at one point the leading candidate to head up MySpace Music, which launched last fall, and the two sides held extensive conversations.

But Van Natta, like many other potential hires for that position, bristled at the job’s org chart: Rather than a standalone company, a la Hulu, the site News Corp. set up with GE’s (GE) NBC, MySpace Music is simply a unit of MySpace, reporting to DeWolfe. MTV executive Courtney Holt eventually took the job.

But Van Natta’s fate has remained closely intertwined with MySpace anyway. Project Playlist, the free music-streaming site he took over last fall, has seen traffic plummet after MySpace, along with Facebook, cut off the site’s access to their users, a move prompted by lawsuits from several major music companies.

Van Natta has made some headway at extracting the company from its legal mess, which predated his hiring, and he has hammered out a settlement with EMI Music Group. But Playlist is still being sued by Warner Music Group (WMG) and Vivendi’s Universal Music Group, and even music sites that aren’t in legal trouble are struggling to keep their heads above water. Plenty of Silicon Valley watchers wonder why Van Natta landed at Playlist in the first place and think that he has been looking for a way out.

Here’s a video of DeWolfe talking with BoomTown’s Kara Swisher a little more than a year ago when MySpace opened a new office in San Francisco. Below that is a video of Van Natta talking to Swisher in 2007 about Facebook’s ill-fated “Beacon” project.