[ChewingPencils]

I've been having the same issue ... I first noticed that the sync error would occur only when I had previously closed OmniFocus on my Mac. In my case, I can get sync working again on the iPhone (iOS 4) by activating the 'recently used apps' and closing OmniFocus. When I launch the app again, sync works fine. Seems to me the issue was introduced with Fast App Switching support. Maybe OmniFocus on the iPhone needs to check for any changes to the sync server when it is launched.

For what it's worth, I also tried syncing with the Cellular Data option turned on and off, but neither option allowed OmniFocus to resolve the sync server.