we had the same problem...(e-mail PDF from print preview only worked once)
Because this was in a situation where users connectec with ica-client to citrix, we supposed it was related to citrix... but tests afterwards made clear it is Outlook2007-related.
Send a test project to PCsoft... no solution until now
We do have a work around for this problem: Supposing Outlook has been started, we do a openoutlooksession & closeoutlooksession in the project initialisation.
Strnage, but after this everything works fine