In our experience this is normally due to the customisations in use with Arbortext. Are you guys using customisations?
You can test if that is the problem by either temporarily removing the "custom" folder (if your customisations are there) or by temporarily clearing the APTCUSTOM environment variable (if your customisations are pointed to from there).
Gareth Oakes
Chief Architect, GPSL
www.gpsl.co