Hi there,
Not sure if this is the correct answer as Im just going by what I read (funnily enough I just found this post while looking for the instructions for my alarm).
The manual says that the alarm can either turn chime mode on (allows you to test what zones are what) or can prevent the user from setting it when it is due for a maintenence check. This may be your problem, the solution looks to be to get the original installers to come out and service your alarm.
The latest manual can be found here...
www.texe.com/document.php?docid=140
hope that helps.
Regards,
AJB.
AJB
April 2007