I now have two new systems with this issue, both XP, both significantly infected with malware. I've done:
Full runs of NOD32 and Malwarebytes till they came back clean
WinsockXPFix
ipconfig /flushdns
netsh winsock reset
netsh winsock reset catalog
netsh interface ip reset C:\log.txt
netsh interface reset all
netsh firewall reset
Complete removal and reinstall of Firefox
I've also removed the network card from device manager and re-added it and tried known good static addressing.
Local RDC and file shares are accessible, and I can ping anything on earth succesfully.
I can't access anything on the web (IE, Firefox, Chrome, NOD32 updates, Win Updates)
I also can't access the local web config pages of anything. Error messages are as follows:
Chrome: Error 102 (net::ERR_CONNECTION_REFUSED): Unknown error.
Firefox: The connection to the server was reset while the page was loading.
IE: Internet Explorer cannot display the webpage
I'm getting ready to call it for the night, but if anyone has any suggestions, I would be quite grateful.