Using iCal linked with Apple's online MobileMe service is one way to synchronize your calendars across devices and make them available online wherever you have an Internet connection. Despite the benefits of this, a number of users have recently run into a problem in which setting alarms on future events results in an access-forbidden error that seems to pop up randomly.
For people experiencing this problem, if you create an event seven or more days in the future and then create an alarm or reminder for this event that occurs seven or more days in advance, iCal issues the following error message:
This may start happening if you enable MobileMe syncing on certain devices, but so far no specific feature or step seems to be causing it. Furthermore, not all MobileMe users appear to be affected.
According to Apple support (e-mailed to us by MacFixIt reader Scott), the problem is being investigated and the company hopes to have it resolved soon. Meanwhile Apple does not recommend trying to troubleshoot the issue as this might result in further configuration problems, especially since the MobileMe team is likely addressing the problem in the servers.
If you are experiencing this problem, your best bet for now is to remove alarms on all events that are set to go off more than a week before the event starts.