if you have everything synched with your PC or you have made a backup of your blackberry, what I would recommend is to wipe the calendar database.
the way you can do this is by going into Desktop Manager > Backup/Restore > Advanced > on the right hand side window, locate calendar, click on it so it's highlighted, and click on clear > press ok to the message.
The database will be wiped out (ie you lose all your data). You can then either perform a selective restore again backup/restore > advanced, load your old backup file from the file menu on the LHS click on calendar, press the right arrow and accept.
if you have synched it with your mail program (such as MS outlook) you can perform a sync to get your data back.
I am having the exact same problem with my calendar. I am running through an Enterprise server and use Lotus notes with wireless calendar sync. I tried following your instructions, but on the advanced screen, "Calendar" is greyed and you can't click on "clear." Any other suggestions?
Also, if you let the BB think enough before giving up and doing a soft reset, it generates the following error:
uncaught exception: java.lang.outofmemory error
After the error appears, you have no choice but to pop the battery and let it start up again.
I did the same and just wiped it all out. First attempt didn't work. I actually had to downgrade to the old 4.0.0 and then re-upgrade to 4.0.2. It's working fine now.