Not my area of expertise, but I've heard of no self-cleaning viri - that would be a real b*tch. I don't think an executable file can delete just itself leaving everything else.
Ask your ISP if they traced it to your IP address or just your e-mail address. The latter proves nothing, as I said before.
There are some (like TROJ_MTX) which block anti-virus sites access, and this is also one of the most effective harvesters. It permits a website to access the infected computer at will. And the infected computer can be any one which has you in its address book. You do not have to have opened the attachment yourself, although I think you would have received the infected mail. Did you ?
http://www.antivirus.com/vinfo/virus...TROJ_MTX.A.DLL