Two users are having the same intermittent issue with their calendars. They
both operate a Windows XP SP2 machine with Office 2003 SP2.

On occasions, Outlook's calendar will not allow the user to do anything in
it, this includes, creating appointments/all day events, viewing existing
items, deleting, etc.

When you (normally) double click or right click and select 'New Appointment'
a window will popup and you can input the details in, but on these two,
nothing happens. You double click and get nothing, no error message, no error
tone, no other kind of popup.

Both users calendars will work if the computer is rebooted, but this is only
a temporary workaround as the problem occurs again soon, possibly an hour
later, sometimes a day or two.

Is there anything anyone can suggest?