Thanks for all the reports. Unfortunately, Google Sync has been undergoing an unplanned maintenance this afternoon, and we have been working to fully restore the service. This has affected Gmail, Calendar, and contacts sync on all devices today since 10am, PST. Our primary focus is to get the service 100% stable again for all devices, and we’re concurrently running tests on iOS4 specifically to troubleshoot any particular issues with the upgrade.
Again, we appreciate your patience as we work to improve Google Sync.