Did private banks lie about the extent of the auction-rate securities market meltdown in February?

That’s when the main dealers in that market stopped supporting the auctions, causing them to fail for the first time in the market’s 20-year history. Now, throngs of private investors who parked their cash in those securities, believing their money was safe, are being told they can’t get it out—and worse, that the securities have actually fallen in value. What is my exposure?