Open directory users cannot connect to iCal.

Lion 10.7.5 server. I had to export users and groups, take it back to a stand alone server and then recreate the OD master and import groups and users and reenter passwords. Filesharing works and the Wiki server works (and can be logged into) but users can't connect to iCal.

I get a message that iCal found the CalDav server but couldn't login with username xxxxx. Please make sure you the username and password are correct.

The uids and guids are the same as they were previously. Is the iCal server storing some other identifier on users that would not have been restored with the import? Is there a command for rebuilding the iCal data or similar?

Any thoughts on where to look or what to try would be greatly appreciated.

Thanks.

Dave.