system
2
Welcome to the forum luiz.
There is a bagle rootkit making the rounds that could be the cause of your problem (possibly two variants, actually).
Please try scanning with F-Secure Blacklight
http://www.f-secure.com/blacklight/
and if that doesn’t solve the problem try a Panda on-line scan
http://www.pandasoftware.com/products/ActiveScan.htm
Please let us know if this works and if you are able to isolate a sample of the malware.