I found this bizarre:
Users where getting prompts to logon (I have a Portal, with Active
directory) on one site. The site would not take their logon
credentials. I recreated the site from scratch..no issue till I
uploaded their documents. The Documents have been scanned on the
desktop and are fine.
Now they can't logon again. I played with the new site, and discovered
only people with (administrative rights) specifically:Manage website
can logon.

The default "manage site groups" have not been changed (reader,
contributer, webdesigner, administrator). I suspect the virus scanner
mcaffee portalshield 1.0, but am not 100% certain. The virus scanner
won't uninstall ...Any other ideas?