So the title is a bit cryptic, but I ran into an issue where a certain blackberry decided to no longer sync it's contacts with our newly migrated BES server. No idea why, tried rebooting the phone, toggling wireless sync of contacts, etc etc... no luck. The user had a bunch of stuff on the phone, so I didn't really want to wipe it or reactivate it particularly. Found this little tidbit of info on Expert's Exchange at:
All you need to do is go to Options > Advanced Options > Enterprise Activation and in the email field press and hold the ALT key and type CNFG. Once you enter this a hidden menu will appear and you need to change "Wireless Sync" to No, now exit this menu and wait 30 seconds and repeat the process but turn sync back to Yes. Once you've changed this setting you will see a slow sync will automatically start and it will repair all the wireless sync settings. In the rare case that this fails you just need to wipe the device and reactivate.