Running BES 4.0 Users have 7510s and 7520s. The 7520s are the ones I'm concerned with. The handheld is running v4.0. In the desktop manager under PIM the calendar is set to BB Wireless Sync. Wireless Sync is enabled on the handheld. If a change is made on the handheld....nothing happens on the desktop. Help

Have you checked the Sync logs (provide logging was enabled) to see if any OTAC activities are recorded for the users with the issues. The logs would indicate if the devices are acknowledging the requests sent by the server for updates. In those same logs you would also see OTAFM activity....inbox folder activities. If no activity is observed for these users try "resending" their service books.

How do I enable logging? Where do I view them? On the server or client? Is there anything to configure on the server to enable the wireless calendar sync? When I look at the user account I see that wireless calendar synchronization is enabled. I resent the service books a couple of days ago. Everything else is working fine.

You can enable logging on the server by starting the BlackBerry Server Configuration. On one of tabs you will see the options to configure/set logging at various levels. The BM, which is separate from the Configuration Manager, can be used to check the "global" and "local" settings on the BES server. I believe wireless calendar sync is enabled by default for every user that's added to the BES.
Depending on how your BES install has been done you should expect to the logs in the following....example D:\Program Files\Research In Motion\BlackBerry Enterprise Server\Logs. They may be identified by the following- 20050511- description (yyyymmdd).

There is a known issue with wireless calendar synch. It is an intermittent fault that does not seem to happen with everyone. RIM are currently working on a fix. Things to note, ensure that the Besadmin account has Service Account permissions at the Site and Configuration container levels. This shoud also filter down to the Information Store level also, but you can do a check to make sure. Additionally ensure that you cdo.dll version on you BES server matches the one installed on your Exchange server.

How do I determine that the cdo.dll files match?

mdelia;
Using File Explorer, right click on the file and choose Properties, then click on the Version tab.

and do the above on both the Exchange server and the BES server, obviously. the file should be located on c:\program files\exchsrvr\bin (drive letter and path may vary on the Exchange server, depending on your configuration for installing apps).

i do know that the BES is hard-coded (or was as of 4.0 but not sure if it was fixed for later service packs) for the above path for CDO.dll. you should also place it in %windir%\system32 for shits and giggles.