Seems like a new craftly little trick:
This happened to me twice in the same day from two different sites.
Apparently this doesn't require any specific access from any of my anti-spyware/addware/virus/malware software, and basically just does it on its own right away.
When going to a site, it edits a value in your registry to block off your task manager. - ctrl+alt+delete will give you an administrator error.
The tasklist/tskill still works in dos, however there's a very quick fix I found here:
http://windowsxp.mvps.org/Taskmanager_error.htm
-aintel

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