Cannot open user designed form

[Darren]

Please help.....whenever I try to send a user designed
form, I get the message "Failed to start the expression
service. The expression service might not be installed.
The problem may be resolved by using Detect & Repair on
the help menu or by re-running Office XP setup".

The form used to work fine. It still does work fine on
other workstations (Outlook 2002) and if I create another
user defined form, that works as well. But I do need to
use this one.

I have tried Detect & Repair, and re-installed, but no
help.