If you were one of the early 2.0 firmware adopters that tried it yesterday before the official release, you may also have the problem where you sporadically receive incoming calls. Sometimes they work. Many times, they go straight to voicemail. If this happens, try the following (it worked for me):
(1) Turn off "Push" in Settings -> Fetch New Data
(2) Also go to the bottom and click "Advanced" and turn off MobileMe push
(3) Under Settings -> AIM, turn on "Sign-off on Exit"
It seems that non 3G iPhones cannot send/receive data while on the phone and vice versa (maybe a regional thing?). So if push is on, it seems to keep a data connection alive.
Once I did the above, I could receive call again.
(1) Turn off "Push" in Settings -> Fetch New Data
(2) Also go to the bottom and click "Advanced" and turn off MobileMe push
(3) Under Settings -> AIM, turn on "Sign-off on Exit"
It seems that non 3G iPhones cannot send/receive data while on the phone and vice versa (maybe a regional thing?). So if push is on, it seems to keep a data connection alive.
Once I did the above, I could receive call again.