What??? Another downgrade of collateralized debt obligations? You mean that they are not worth as much as you previously thought? Weren't they all AAA? What happened? What did we miss

Feb. 5 (Bloomberg) -- Fitch Ratings may downgrade all of the $220 billion of collateralized debt obligations it assesses that are based on corporate securities because of rising losses.

The New York-based company may lower the notes by as much as five levels after failing to accurately assess the risk of debt that packages other assets, according to guidelines proposed by Fitch today. CDOs with AAA grades that are based on credit-default swaps and aren't actively managed may face the steepest reductions.

Ratings firms are responding to criticism that they failed to react quickly enough as increasing defaults on subprime mortgages in the U.S. caused a plunge in the value of CDOs. Fitch, a unit of Fimalac SA in Paris, lowered $67 billion of mortgage-linked CDOs in November, slashing some AAA debt to speculative grade, or junk.