I've had the same dns problem twice. The first time it was fixed really easily by calling ur ISP and just asking them. They reset something and it worked after that. Can you still ping your two computers that are on the same network? If so you should be able to copy your important info onto the computer that does work. Try formatting your entire hard drive and reinstalling everything from scratch. That worked for me. If that doesn't work than at least we know that its a hardware problem and it has nothing to do with software.
Threaded Mode