I've been fighting network and graphis issues since Beta 41, and I *think* I have the fix, at least in WinXP Pro, though I only have a limited data set to prove it.
For some reason AH doesn't like having IEEE 802.1x authentication turned on. It's not JUST authentication, but that's the part that'll cause problems. If you're having network/stutter/HCL/CTD issues you might try turning this off and see if it helps.
I've been stable on line for the first time in quite a while tonight. Wheee!