I'm running BES 4.0.4 on a Windows 2000 Server (SP4) which is running Exchange 2000 (SP3)
Our exchange mailboxes are running on a Windows 2003 server (SP1) running Exchange 2003 (SP2)

I've copied the CDO.dll (6.5.7638.2) from the 2003 server to the BES server (c:\program files\exchsrvr\bin) and registered it, and have enabled wireless calendar sync on the BES server, and for individual users, but it's still showing up as disabled in the user list view, and isn't working. Anyone got any ideas?

On the handheld, go to Calendar, click the trackwheel, choose Options and see if Wireless Synchronization is listed. If it is, set it to Yes. If its already set to Yes, set it to No and save the changes. Wait a few minutes then set it back to Yes.

It's not listed...

The handhelds model:
7290
OS Version V3.8.0.139 (1.8.0.99)

Since its OS 3.8, you'll need to enable it within Desktop Manager. Open up Intellisync and then the PIM options then change Calendar to BlackBerry Wireless Sync.

That's worked, Thanks. I assume the BES detects the OS version and the enabled/disabled listing changes based on that?

I had the same problem using the handheld software ver. 4.0.0.160 on a 7510. Turned out that there is a new release of the software that has a fix to show the wireless sync in the options of the calendar. Upgraded to ver. 4.0.2.54 to fix it.