then you have a compromised version of firefox. Delete it and redownload. Assuming you're using a trustworthy antimalware program that is.
Hmm... perhaps this is what's causing your USB related problem as well? Here's a Yahoo! Answers querry on Malware.sality for you: http://webcache.googleusercontent.com/search?q=cache7QOcLW8T_QJ:uk.answers.yahoo.com/question/index%3Fqid%3D20091028103112AAV8aW0+malware.sality&cd=1&hl=tl&ct=clnk&gl=ph Sad thing is according to most of the posts there the best course of action for you would be a full Hard Drive re-format