Well, like most people I, too, have lost all networking after upgrading to beta 6. But now I got networking back thru my wireless on MBP. All I did was change the Network Adapter from Wireless to Default Adapter. Booted XP up and voila, netwoked worked again! Hope this helps. Update: Nope, it really wasn't working. IE was displaying Cached pages. Shucks..... Sorry about that.
As others have discovered setting addresses manually corrects the issue. http://forum.parallels.com/thread1248-4.html