We recently fixed bug 479867 which does a quite invasive change to the database schema. The change itself is simple, but since the existing cached calendars need to be migrated in some form, it got quite tricky.
If you are having trouble with the upgrade, please leave a comment here or file a bug. Things you should do first:
calendar.debug.logand check for any storage related messages
- Remove or rename
The cache is automatically regenerated if it does not exist. To find your profile,
see this page
Please also describe what kind of events you have in your calendar (lots of events? more recurring events, or more single events? Accepted invitations?), what kind of calendar you are caching (caldav, google calendar, ics) and what error message you are getting.