Try running your scans again in Safe Mode. To get into Safe Mode, reboot and then either hold down or tap the F8 key repeatedly while the computer is starting up.
Sometimes malware can copy itself and hide from security products. Running the scans in Safe Mode could help identify those that avoid detection.
You may also want to try running Superantispyware as well. It is an excellent tool and also can detect some malicious programs that other products miss. There is a free version available at the link below:
http://superantispyware.com/
After cleaning your system, disable System Restore, reboot and re-enable System Restore when you log back on. This will clear the malware that may still be lurking in System Restore, which could be reinstalled should you need to rollback at some point. Additionally, a reboot may be required to complete the malware removal process. For reasons this should be done after and not before malware removal, see the webpage below:
http://msmvps.com/blogs/spywaresucks/archive/2005/09/17/66724.aspx
There is one final possibility which would be that your passwords have been cracked. After ensuring your system is completely clean, you should change your passwords and secret questions.
Take precaution when using messenger products. If a contact is infected, they may unknowingly send out malicious links and attachments. When you open them, malware can again be quickly reinstalled. Always confirm that you contact actually sent you the information before open. An even safer method is to go into your messenger options and disable urls as well as attacments.