This is a long shot but has anyone here had any problems after installing the latest cumulative security update for Internet Explorer 6 SP1 (918899), under either Win2K or WinXP, available at the Windows Update website? Given the number of caveats it has when you click on the details, I'd be surprised that anyone's PC would still work properly, after installing it (I'm exaggerating, of course).
Seriously, though, the number of known issues that Microsoft admits can arise from installing this update is not inconsiderable. See
http://support.microsoft.com/kb/918899.Am I being paranoid?