http://ftalphaville.ft.com/blog/2008/05/21/13198/ft-alphaville-exclusive-moodys-error-gavetopratings-todebtproducts/

"Internal Moody’s documents seen by the FT show that some senior staff within the credit agency knew early in 2007 that products rated the previous year had received top-notch triple A ratings and that, after a computer coding error was corrected, their ratings should have been up to four notches lower."

http://www.ft.com/cms/s/0/09a762ee-2699-11dd-9c95-000077b07658,dwp_uuid=5fd271ee-61f6-11dc-bdf6-0000779fd2ac.html

But is it as simple as a simple bug, or is their method of modelling CPDOs flawed

http://www.noelwatson.com/blog/PermaLink,guid,136d4b18-8d46-4687-8a83-0ef2f97ab805.aspx