"One of my calendars wasn't syncing and this solution worked.
Settings > Applications > Manage applications > Hit the Menu Button > Filter > All > Calendar Storage > Clear data > OK
This will clear the saved calendar data and the next time you open your calendar app, it will re-sync your calendars.
Settings > Applications > Manage applications > Hit the Menu Button > Filter > All > Calendar Storage > Clear data > OK
This will clear the saved calendar data and the next time you open your calendar app, it will re-sync your calendars.