Calendar Sharing Error Message

Hi,

I am having difficulty sharing my calendar, which I am running through Outlook 2007. If I attempt to change my calendar sharing permissions it allows me to go through all the usual steps:

• I right click "Change sharing permissions"
• I change the permission level for a particular Name (I've tried a range of different permission types)
• I click "Apply"
• I click "OK"

After thinking for a few seconds, my computer gives me the error message "An error occured when setting schedule permissions."

Is anybody able to give me advice on this one?

Thanks very much,

Paul