Blackstone Capital Partners V LP, which at $21.7 billion is the largest private equity fund raised thus far, was held at 20.5% below cost. Blackstone V deals include Hilton Hotels Corp., which has struggled with the downturn in the hotel market. The firm bought the hotel chain for $26 billion in 2007, and included $1.4 billion in equity from Fund V. Blackstone also participated in the Harrah's deal, injecting $137.5 billion of equity out of its Fund V, which likely contributed to the fund's write-down.

Meanwhile, Kohlberg Kravis Roberts & Co. has reportedly asked investors in its European Fund II, a 4.5 billion-euro pool closed in 2005, for at least an extra 400 million euros ($530 million) to fund potential debt restructurings and equity injections. KKR has spent most of the fund, leaving inadequate cash to support its investments.

KKR, like many buyout firms, has struggled to sell assets as investors shy away from initial public offerings and the credit crisis impedes asset sales to other private-equity companies. Investors in European Fund II have until May 13 to participate in the additional money pool.

Also, KKR has again delayed plans to merge with its publicly traded European fund, KKR Private Equity Investors LP, and list the combined company on the New York Stock Exchange. The firms had put off the merger in November, citing the credit crisis. The deadline to complete the transaction is now Aug. 31.