There may be remnants left of the virus, or the initial infection may have corrupted some of the files. It might be a good idea to run some additional scans with AV's, just to be sure it's gone.
Malwarebytes Norton Power Eraser
(Be sure to run the rootkit scan option with this tool)
Quote:
Because Norton Power Eraser uses aggressive methods to detect threats, there is a risk that it can select some legitimate programs for removal. You should use this tool very carefully.
Keep in mind, you may have to do a repair install, or worst case scenario, a complete reinstall.
Repair Install Clean Install Windows 7