Outlook 2003 Calendar issue

[Superbobu2]

I have a client using Office 2003 with updated SP. She views severals peoples calendar from her outlook. When viewing 2 particular calendars she keeps getting the following message:

Unable to open calendars in Outlook. Message displayed is: There is not enough memory to perform the operation.

It has happened on different PCs. No errors in event viewer. Recreated her outlook profile and still gets error. Updated SPs on the calendars she is viewing. So all users have Outlook 2003 with SP3. Anyone ever see this and know the fix?

thanks