All ports appear blocked

Recently tried Charter as the only other ISP in my area sucks absolute balls.  However, uTorrent doesn't work, and port checker tests reveal that nobody can access ANY ports on my computer.  Three different websites, checks on common ports and random ports.  EVERY port is apparently blocked.  I called Charter about this but half of them say Charter doesn't block anything, and the other half don't know what ports are.  I only have Windows Firewall and for the tests even that was disabled.  I didn't connect it to a router, my computer has a straight connection to the modem.  I even tried it with another computer of mine.  (one's Vista, one's XP).
Any suggestions?  Internet with AT&T cuts out three times a day, and Charter's the only one I got left.

>>12
I can't explain it.  Obviously I can access html but port checkers say port 80 is blocked.  It makes no sense. 
>>13
and how would I go about identifying on which hardware this firewall was located, and how to disable it, or what to do if it is a proxy server on Charter's side?