The Calendar Menu .net application will only launch when you have a single menu showing on your main menu. If you launch SchoolBase with multiple menus the calendar gives this error:

SchoolBase was unable to complete your request
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User No.: 5
Occurred: 23/03/2010 14:29:24
Location:
Origin:
Type: Unknown
Message: Invalid use of Null
Error No.: 94
SB version: Version 3.10.02
Access version: 11
Windows version: Windows XP Build:2600 Service Pack 3
SQLServer version: 9
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Do you wish to report this to Furlong Business Solutions?

To work around this simply select a single menu with Calendar in it.