I can understand your reluctance to try this again soon!
Loss of network connectivity as a consequence of malware removal is a known
side-effect of both antivirus and antispyware removal. There's a kb article
about this for Microsoft Antispyware. Each new generation of the product
has been changed to lessen the occurrence of this side-effect but it does
still exist.
On XP, SP2, fortunately, there's a simple fix:
at a command prompt, do:
netsh winsock reset
and hit enter, and restart the system.
This would be what I would expect might be the cause of your issue, from the
description. It is also possible that what you saw was a false positive for
a component of your network software--we've seen some reports of those too.
The best preventative of that issue is to make sure you are running the
latest software your ISP has for your hardware, and, in general, give
Windows Defender some time so that the false positive might be removed from
the definition set.
If you really want do do some digging--the System Event log, filtered by
source "windefend" will have all the entries showing activity by Windows
Defender--including precisely what was detected and removed. There's even a
clipboard button to allow posting the individual records--and that might be
valuable in terms of preventing this happening in future.
You can open the event log:
start, run eventvwr.msc <enter>
Click on System, click on View, Filter, click on Source, choose windefend,
go back to the time of the original scan, and spot yellow-triangle entries
showing the precise detections involved.
Thinking about this--I'm about 50/50 on what may have happened on your
system. We have seen reports of a false positive for cable-modem related
drivers, and there is the known issue of winsock breakage--it'd be good to
know which you ran into.
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