I can restore my Internet connection by opening the command prompt and typing "ipconfig/release" and then "ipconfig/renew" This keeps it working for another 10-15 minutes. Furthermore, I think it's a DNS issue because once the Internet "goes out" I can still access web pages by typing in the IP address of the site... so www.google.com will not work, whereas http://126.96.36.199/ will.
My first thought was spyware/viruses, so I did everything in the Malware section's "Do this BEFORE posting a HiJackThis log" with no results. After doing a little searching I found a few people encountering similar problems, with various problems... most people who encountered these problems had installed either ZoneAlarm or Cisco VPN, neither of which I have.
Please let me know if anyone has encountered this, and if so, if you've found a permanent solution.