Are you sure I must delete the entire Cache folder?
Must you? No. It is simply the most expedient method of eliminating all the variables.
You can remove the files that refer only to iCal. However there may be other files affecting iCal that are not labeled with the name "iCal", which is why I pull the whole thing.
Read more about caches here:
http://en.wikipedia.org/wiki/Caches. They are re-created upon restart in the Mac OS. The only downside I have noticed in my years of pulling cache files for issues is that the programs that had caches in there will run more slowly the first time you launch them after pulling. Subsequent launches will be back to normal. That said, I don't pull them for fun. Only pull them when you are experiencing issues (like you have now).
If you have any concerns, pull just the ones labeled "iCal" keeping in mind what I said above about other applications being involved not labeled "iCal". You should of course also have a backup at all times of any data you consider important:
http://support.apple.com/kb/HT1553
Personally I use Time Machine to an external hard drive to handle my backups as well as occasional CD burns of more vital data (More backups = better when it comes to REALLY important information).
What about the other applications that reference it?
They will rebuild their cache file the next time they are launched.
