I tried IE8 with Windows 7 and it kept:
1. Occasionally telling me my networking was unavailable hitting simple sites like google.
2. Not letting me download files from the MS site.
Switched to Firefox 3.0.5, and it's worked perfectly.
I did, of course, file bug reports, since both are beta products.
Not done, but I'm not sure it was only related to IE8, since this is also on the Windows 7 beta.
- zevo