mj.hall,
Welcome to Apple Discussions.
Since this is your first post, you are not aware that adding your question to another posters question is known as
Threadjacking. Additional questions dilute support for both the original poster and the threadjacker.
The circumstances involved in your problem may seem similar, but individual attention will be provided if you start your very own thread.
When you start your own thread it will be helpful to provide the following information:
Do you have any iCal backups?
Are you using any iSync features?
When did this behavior start?
Will iCal work in another user account?
How did you reinstall iCal?
Did you reapply the Combo Update after reinstalling iCal?
;~)