By Katie Benner

If you’re Lehman Bros. (LEH), the market has doubts about your balance sheet, your stock is down, and rumors say you’re going out of business or bound for the auction block. So forming a hedge fund that looks like nothing more than a place to dump unknown assets might not be the smartest idea.

But, reports Bloomberg, this seems to be exactly what Lehman has done. The firm has sold $4.5 billion worth of assets to a newly-formed hedge fund that counts Lehman as a significant investor; is run by seven recently-departed Lehman executives; and operates out of Lehman office space, three floors down from the office of Lehman’s corporate secretary, the report says. What’s more, Lehman is keeping its dealings with the fund, R3 Capital Partners quiet, and it isn’t mentioned in the firm’s Securities and Exchange Commission filings.

You don’t need to know much more about R3 to see that this could be cause for alarm.

Lehman investors will want to know how any transactions with the fund have affected the bank’s financial statements. R3 told Bloomberg that it is “an independently managed fund in which Lehman Brothers is a limited partner and holds a passive, minority stake in the general partner.”

Not good enough for a firm that wants to restore investor confidence, says Bloomberg. “That [statement] won’t keep investors from forming their own conclusions. If Lehman doesn’t like what they decide, it will have only itself to blame.”

There is no dearth of potential culprits responsible for the current financial meltdown — ratings agencies, greedy bankers, a housing bubble, Alan Greenspan… the list goes on and on. But Steve Schwarzman, founder of private equity titan Blackstone (BX) would like to add an accounting rule to the list.

According to The New York Times Dealbook, Schwarzman has been privately arguing for weeks that the rule known as FAS 157 is forcing bookkeepers to overstate problems and is making financial firms look wobblier than they are. Blackstone’s president Hamilton “Tony” James says FAS 157 is “dangerous.” There is even a campaign afoot in Washington to change the rule, according to the Times.

The controversial hypothesis has been posited by others, and this is how it works: FAS 157, which went into effect just as the credit crisis was really heating up in November, requires accountants to mark hard-to-value assets at the prices they would fetch on the open market. So if a security once worth $100 could only sell for $50 in the market, a company’s books have to reflect that lower value. Here is where Schwarzman cries foul: The accounting rule forces a writedown of this size even if the actual value of the underlying assets in the security have only declined by, say, 15%  (so, for instance, a pool of home loans is deemed to have fallen in value by 50% even if the price of the homes behind the loans have fallen 15%). If there are no buyers at all, then the security has to be deemed worthless.

As a result, Schwarzman argues that some of the writedowns that have since occurred have been based on theoretical losses which may never become actual losses. Because of the rule, however, banks have been forced to raise billions of dollars in new capital to offset these paper losses.

Schwarzman’s theory works only if the underlying assets are really worth more than the market will pay. As Dealbook points out, “if they are so mispriced, why isn’t some vulture investor – or Mr. Schwarzman – buying up C.D.O.’s en masse?”

FAS 157 proponents say that if we do away with the rule, known as mark-to-market accounting, then financial companies will value securities at prices that suit them. Some say that Goldman Sachs (GS) proves the need for the accounting rule: the investment bank has long marked to market prices, which is why its risk officers were able to hold back eager traders from making bad bets when everyone else was riding the mortgage-backed security bubble.

Lehman Brothers (LEH) is under fire again. David Einhorn, a highly regarded hedge fund manager who is betting against Lehman by selling its stock short, gave a speech this week renewing questions about the quality of the firm’s first-quarter earnings, which Lehman reported in March. The market mostly liked the report at the time it came out, but Einhorn has questioned Lehman’s outsized unrealized gain on an equity investment and wondered why the firm hasn’t taken a larger writedown on its holdings of collateralized debt obligations, or CDOs, The Wall Street Journal reports.

Lehman rejects the notion that it has any accounting issues, saying Einhorn “cherry-picks certain specific items from our quarterly filing and takes them out of context and distorts them to relay a false impression of the firm’s financial condition which suits him.” But Einhorn’s scrutiny of the firm comes just days after the Journal reported that Lehman had a tough second quarter as well. The firm is looking at $1.5 billion to $2 billion in second-quarter losses on failed hedging transactions and asset writedowns, the paper reported. On Thursday, Ladenburg Thalmann analyst Dick Bove downgraded Lehman and two rivals, saying he expects their shares to drop 15%-20% from current levels as the firms struggle to produce adequate profits, due in part to their failure to adequately manage risks tied to the volatile markets. In a reminder of the firm’s brush with liquidity worries after Bear Stearns (BSC) collapsed in March, Bove says Lehman is “the most vulnerable.”

Former UnitedHealth (UNH) CEO Bill McGuire is in a giving mood this holiday season. The executive, who left the company last year under the cloud of an investigation of the HMO’s accounting practices, agreed Thursday to give back more than $400 million worth of stock and benefits to settle a shareholder lawsuit against UnitedHealth. McGuire also agreed to settle a Securities and Exchange Commission civil suit tied to the matter, The Wall Street Journal reported.

UnitedHealth had to restate earnings last year to fix its accounting for hundreds of millions of dollars in stock options that were doled out to McGuire and other execs at a discount to the existing stock price — handing them windfall gains. Back in April 2006, when the so-called backdating scandal came to light, McGuire’s stock option haul was worth an estimated $1.6 billion. Though McGuire insisted throughout that UnitedHealth had engaged in no backdating, a law firm hired by the company later ascertained that “certain facts run contrary to this assertion.” Seems like that’s always the case in CEO land, though.