Posted 18 May 2010 - 06:23 PM
Well, I found the problem. Turns out that the spyware/malware must have been partially removed, and left some baggage at the door. The LAN settings for IE had a proxy server address defined for HTTP requests. Its value was 127.0.0.1 port 5555. The "Secure" proxy server address was not defined, and therefore HTTPS requests went out OK. There must have been a program running listening to port 5555 for HTTP requests, and doing its dastardly dirty deeds before forwarding the request on to its final destination.
I found this out rather serendipitously. When installing SpyBot, it failed to "phone home" for updates, and the error message generated by the SpyBot installer highlighted the failed 127.0.0.1:5555 attempt.
It's too bad that the spyware/malware removal programs are not looking for these localhost proxy server settings - and, at the least, issuing a warning.