Constant network error in 11.04

Hello, community. I have a really SERIOUS problem in Ubuntu 11.04 (or Natty Narwhal). I upgraded it from an install of 10.10, which was installed through Wubi. Until recently, the 11.04 install was running perfectly. The problem is that, daily, I get a network error. What happens is that the network indicator disappears, then suddenly, I see a DNS resolution error in Chrome. I checked all internet-facing programs, and they fail to get a connection. I also check my router and cable modem, and there is no problem there. This is a recurring problem; usually, I get a few hours of uninterrupted surfing, then it occurs. I reboot, then it repeats. This has gotten so bad, that I have had to use Windows
(gasp!). Why is this occuring? The only reasons why I would see this problem is that I have the firewall on or that I use an alternate DNS provider on Windows? I have already changed my DNS settings on Windows to that of my ISP's (default) and it still occurs! As a side note, this problem never happened on 10.10.