Blackberry7100 decryption errors

I have a blackberry 7100 decryption error message when I recieve emails from the exchange server. I have been with tech support and have tried alot of different options such as deleting the research and motion folder in the registry, generating new encryption keys, deleting and reinstalling desktop software, deleting info on exchange server, hard and soft reboot on the blackberry. Can you guys think of any solutions that tech support might have missed. Can you guys tell me any prior experiences you have had with blackberry issues with decryption errors when recieving emails???