Three weeks ago I warned that you should review the holdings of your money market funds because they could be exposed to the mortgage mess. Well, today the Wall Street Journal reports that several money market funds are taking action to shore up their holdings because of exposure to one of the troubled SIVs -- Cheyne Finance LLC, which was downgraded to default status last month by S&P after the SIV went into receivership.

Bank of America (NYSE: BAC)'s money management arm, Columbia Management, is managing two of the money market funds discussed in today's Journal story - SEI Investments Daily Income Trust Prime Obligation Fund and SEI Daily Income Trust Money Market Fund. In my story three weeks ago, I warned about the SIV holdings in Columbia Cash Reserves Fund. I also warned about holdings in other Bank of America mutual funds managed by Columbia. Other mutual funds holding SIVs mentioned in the Journal's story this morning include STI Classic Funds from SunTrust Banks (NYSE: STI) and Credit Suisse Group money market funds.

All this is finally becoming public because S&P took the position that exposure to troubled SIVs like Cheyne Finance LLC was not "consistent with its criteria for receiving its highest ratings for money-market funds." Money market funds are not supposed to invest in low-grade securities. The big fear for investors and government regulators is that losses in these riskier holdings could drive the asset value of a money market fund below $1 a share or "break the buck." The only time that happened was in 1994 after a money market fund faced losses because of the 1994 derivative crisis.