If your software doesn't seem to be working the way it should be you should probably install the latest patch, which has fixes for any bugs in the system.

ArcGIS
All available Browse all of the available patches & service packs available. On the right hand side of the page is a list of the latest pathches.
ArcGIS 9.0 Service Pack 3 The latest service pack for ArcGIS 9.0 - contains all of the patches up to its creation (March 07, 2005).
ArcGIS 9.0 Map Document Patch Try this patch if you have problems opening up your ArcGIS map document on different machines (over a network).
ArcGIS Desktop 9.1 Map Document Interaction Performance Patch
This Patch solves a performance issue that occurs when interacting with maps while the Effects toolbar is open.
ArcView 3.x Windows XP Patch If you appear to be having problems with ArcView 3.x in your lab, and are using the Windows XP operating system, try installing this patch.