Yeah, I wouldn't *think* it would be an actual corrupt COD, as they have sort of an integrity whereby if the package was damaged then it just wouldn't run per-se. I am inclined to think it's data as jjmach mentions.
One possibility: change the Sync tool to do an ASCII Export to a text file of your device calendar, run it. Erase the on-device calendar (Agenda view, Delete Prior), then flip the Sync to ASCII Import and suck it all back in. (NOTE: past entries are lost, it only exports current and future events. sucky, I know.)
That's my generic idea, but tailor to suit for your personal configuration. You could maybe export your Outlook calendar instead, wipe both Outlook and the device, re-import it back to Outlook then sync the device back up. Or maybe all of the above!
Really depends on your specific setup...