Over the past couple weeks I’ve had issues getting my OSX 10.5 iCal client to continue working properly with our centralized CalDav server. I stopped being able to invite other domain users to my events as well as reserve “locations”, despite all my personal (non-domain) calendars continuing to work properly. I noted these iCal errors in Console.app…

*** -[NSConcreteTextStorage attributesAtIndex:longestEffectiveRange:inRange:]: Range or index out of bounds

CalDAVOperationQueue tried to dequeue operation <CalDAVScanDropBoxQueueableOperation: 0x174eb6a0> but it was not at the front of the queue.

When I tried to delete my domain account within iCal’s preferences, the application hung. When restarted, I could no longer bring up the preference dialog and saw this error repeated in Console…

*** -[NSURL initWithString:relativeToURL:]: nil string parameter

Apparently deleting everything in ~/Library/Calendars and starting fresh is the easiest solution. I have years worth of notes and interesting tidbits that I need to keep, however, so simply deleting all my data was not an option. With some educated guesswork, trial and error, I discovered that the following steps seems to make everything work again without apparent data loss or corruption..

1. Quit iCal.
2. Go to ~/Library/Calendars and backup the entire directory, just in case.
3. Delete all “Calendar Cache” files as well as any directory ending in “.caldav”.
4. Start iCal.
5. It may give you a progress dialog about “Upgrading Calendars”. I think this means it’s rebuilding the cache file.
6. Go to “iCal -> Preferences…” and delete/readd your domain account.
7. Wait for the domain account to resync and you should be go to go.

Hope this helps!