I came across this error today and though I would share with you the quick fix for this. The user was using outlook 2003 and was getting an error message when trying to accept a meeting request. It gave an error of “This meeting is not in the calendar. It may have been moved or deleted.” So here is what you need to do.
1) Restart your computer.
2) Once computer boots back up you need to do a search of the file frmcache.dat and delete this file.
3) Now open outlook backup and you should be able to now accept meeting request.
I also read that if this doesn’t work that you can try and run outlook from the run command and type in outlook.exe /cleanreminders I haven’t tried this but read that this had helped others.
UPDATE: I was also informed that if those don’t work then you need to run a scanpst fix and this should solve the problem. Do a search for scanpst.exe then run a scan on your pst file. To find your PST file, open up outlook then click on file and select data file management. Under filename expand the column and you’ll see the full path and name of your pst file. Now close out outlook and browse to your pst file and run a scan. RG