I am getting the same popups as this user, but I have Symantec Endpoint Protection and I also had ZeroAccess.B warning. http://community.norton.com/t5/Norton-Internet-Security-Norton/Infected-with-Trojan-Zeroaccess-C-and-Trojan-Gen-2-Unable-to/td-p/840110
Endpoint Full scan did not clear it and I used Power Eraser which Symantac suggests for Zeroaccess before finding this thread. Now the popups are gone, but I am still concerned it isn't dead.
Trojans were detected in C:\windows\installer and in random number generated folder that I could not see even enabling everything.
I started following the directions downloading FSS and ComboFix, but am stuck implementing the regedit keys. WIth a fresh reboot, I still get Cannot import: C:\Users...ZaFix.reg: Not all data was successfully written to the registry. Some keys are open by the system or other processes.