I've been experiencing this problem form weeks now. I finally had time to do some research, which is how I found this forum) and found my solution here: BlackBerry Desktop Manager has encountered a problem and needs to close
I used the solution for "Handheld Tools Desktop manager" below and it works now (at least for now)!
The Intellisync folder is corrupt.
For BlackBerry Desktop Manager
1. Close BlackBerry Desktop Manager.
2. Open Microsoft® Windows® Explorer and delete the Research In Motion folder in the following location:
C:\Documents and Settings\<user_name>\Application Data\
3. Open the BlackBerry Desktop Manager again.
4. Double-click the Synchronize icon.
5. On the Synchronize tab, make sure Synchronize Organizer Data is checked.
6. Select the Configuration tab and click Configure Synch. The Research In Motion folder is created automatically.
7. On the Configuration screen, select the Address Book application and click Choose.
8. Select the correct translator and click Options.
9. To save the changes, click OK.
10. Return to the Synchronize tab and perform a synchronization by clicking Synchronize Now.
For Handheld Tools Desktop Manager
1. In Handheld Tools Desktop Manager, select Synchronize.
2. Select Configuration Settings.
3. Click Reset Configuration. The Research In Motion folder will be re-created automatically.
4. On the Handheld Configuration Screen, select the Address Book/Calendar application and click Choose.
5. Select the correct translator and click OK to save the changes.
6. Return to the Synchronize tab and perform a synchronization by clicking Synchronize Now.