If you use the Blackberry desktop software to sync with Outlook, you might want to ignore the offer to update the software to the latest build. It apparently breaks the ability of Blackberry devices to sync with Outlook 2010, possibly other versions as well.
Finding copies of older builds of the desktop software isn't always easy, so restoring an older version may not be possible unless you have a copy of an older version saved somewhere.
Repair Blackberry and Outlook Calendar sync
Use this method to fix most calendar sync problems except for all day events spanning two days, is as follows:
- Backup your contacts data using the desktop manager. Choose the custom backup option and backup the address book only.
- Set one-way sync, to device only, replace device data set to on.
- Do the sync.
- Restore your contacts from the backup.
- Switch two-way sync in the Desktop Manager
- Now Sync again
As a side note, Office 365 E level accounts include BES cloud sync at no extra charge. It works with BES and BIS phone plans to sync calendar, contacts and mail over the air, eliminating the need for the desktop software.