Acad2000 Express tools error

We have a network installation of ACad2000. We recently updated the express tools for this version. Now some of the users are getting the error: AutoCAD menu utilities loaded.; error: no function definition: ACET-CMD-CHECK, upon executing Acad. Acadworks fine after this error except for the express tools. When you try to use the express tools we get the error: Command: layfrz
AutoCAD Express Tools Copyright ? 2000 Autodesk, Inc.
; error: no function definition: ACET-AUTOLOAD. Does anyone have any idea why this might be happening?