Here's Microsoft's recipe for this issue:
http://support.microsoft.com/kb/892350
In general, I agree with Jupiter Jones. A number of programs, legit and
illegit, add themselves to the Winsock LSP stack. When they need to be
removed by informal means, this breaks the stack. This is enough of an
issue that there is a new command in Windows XP Service Pack 2 to deal with
it.
With this product, the breakage can occur because of removal of genuine
malware, or, in some cases, removal of an item which is part of the stack,
by detection as a false positive. The key to knowing which it was is in the
cleaner.log file in the directory the antispyware application is installed
in.
There are a couple of additional sidenotes to the process of cleaning up
after this breakage--i.e. beyond what's in that KB article, I think:
1) legit third-party programs you've installed that hook into the stack will
need to be reinstalled. VPN clients, some Internet Privacey applications,
don't know a full list.
2) you may see an unexpected appearance in the network connections
folder--the firewalled lock symbol may not be there for the connections,
although they say that they are firewalled various places. To resolve this,
go to the Advanced page where firewall is turned on or off for a connection,
and first turn it off, then turn it on again. This should get everything
looking the way you expect.