It looks like this problem is directly related to the permissions listed in the keychain as stated earlier.
Well, this may be the case for you but I did a clean install and I have these problems!
It looks like this problem is directly related to the permissions listed in the keychain as stated earlier.
I have both Airport and System Preferences in the Access Control tab. Do you still select "Allow all applications to access this item," or do I keep it at "Confirm before allowing access?"
Not sure if this has been mentioned, but my testing has narrowed down the wireless problems by and large to the combination of the login panel and a wireless connection with WPA/WPA2 security enabled. Once I enabled automatic login and no login on wake from sleep or screensaver, most (but not all, underline) of the wireless problems were fixed.
The other wireless problem is the bluetooth shutting down intermittently. While I cannot recreate conditions to reproduce this based on something particular, it turns out that a combination of my wireless kbd and mouse is what causes the issue. Resetting the keyboard only (and not the mouse) works for me to fix both the mouse freeze and the kbd freeze. It's even more annoying since I cannot reproduce it, though it continues to happen. Reverting back to Tiger and both of these problems were gone, so I concluded that it's not hardware, either in the BT module of the MBP or the mouse or kbd.
It's ironic that the problem we're trying to fix is all but preventing us from downloading the update!