I performed the indicated tasks, although not in the order you specified, because the pandasoftware and housecall.trendmicro scanners use activeX and hence are dependent upon IE yet the virus prevented me from using IE to run the scanners. Furthermore, those virus scanners would not work with FireFox.

However, after having HijackThis remove the " O4 - HKCU\..\Run: [winpack] C:\WINNT\system32\winpack.exe" entry, deleting the C:\WINNT\system32\winpack.exe file, and rebooting, I did not observe the problem. This enabled me to run the web based virus scanners with IE.

When running the virus scanners, AntiVir found no infections, pandasoftware found one infection associated with fdeploy.exe, and housecall.trendmicro found no infections.

After rebooting, I still have'nt observed the problem. IE works correctly. Considering the intermittent nature of the problem, I will continue using IE and post my observations in a few days. If I don't observe the problem within a few days I'll feel confident it has been resolved. It looks like winpack.exe was the cause.

Thanks!