pedro2, do more virus scans/searches.. I had a similar thing happen to me recently. Turned out I had a trojan horse that sent an email to every email address in my contact list and also wiped out my contact list!!
My friend told me to scan my pc with the top five virus scans listed on a google search of 'free virus scan'. I believe that it was http://www.kaspersky.com/virusscanner
that identified the virus I had. Several others, including the one I paid money for on my laptop did not identify the trojan horse.
PS The email that was sent out did not include any virus, thankfully.