citrix/terminal service - custom form slow

Hi
we have recently developed custom forms that contain vbscript which
is very slow to load. it takes 3 mins for a 5kb form to load up.
The user access their outlook through citrix. The form definitions box
is not ticked so its not a one offed form.
the odd thing is when the only code in the form is a msgbox in the
item_open function the form is slow. if i delete the item_open
function the form is fast.
Has anyone come across a similar problem.