When it comes to wireless calendar the 2 main things to check are:
1. Permissions of the BESAdmin account
2. Version of CDO.dll on both the BES and the Exchange server
Seeing you cannot wirelessly sync calendar from your BB to Exchange then one of the above is the issue.
If the permissions are not set correctly or if the BESAdmin account is part of an administrative group, Calendar will fail to sync from BB to Exchange.
If CDO.dll is a lower version on the BES then you will not get proper communication from BES to Exchange.
You can have your admins review this article: BlackBerry Search Results
Odds are this is affecting more than you as well. Have the admins look at that article and make sure that everything is as it should be and check with more users.
You could also try deleting your Desktop[CICAL] service book and have them resend it from the BES to rule that out as an issue as well.