Today at around 12.30pm PST Fortinet pushed out an A/V signature update that caused virtually every file to be identified as infected with the js/gumblar.gen virus. This was most likely a problem with a false positive in the signature file. Fortinet made a new signature update available by 4pm PST today which resolved the issue.
** Update from Fortinet **A false positive is discovered in our AV Database Version 11.351 on the signature JS/Gumblar.gen.
A new version of the AV Database, version 11.352, has been release to correct this issue around 4:20 PM Pacific Time today (Friday, January 8, 2010).