Can be a dodgy one here...
With regards to the support and commisioning...
If you commisioned the Citrix installers to install a Citrix server and enabling you to connect to published applications etc, then, they could well have done that...
However, if that included installing the application and ensuring that it is available to each client and doesnt fail, then obviously they have not completed that task satifactorily, however... I would be VERY surprised if they commited to that level on SOMEONE else's application that has/has not been proved to work on Metaframe, but hey, if they said they would deliver, then you may have a case, I thought you guys thrived on sueing each other anyway (heh sorry j/k, cheap shot from a Brit...)
Certainly sounds like printer issues rather than the application itself however, (in which case its effectively a Terminal Server issue not application issue with regards to having it fixed) have you tried the printer with any other applications ?
What is this application exactly ? is it an Access database ? or some other application ? how/what/where was it written. All infomation you can provide will help.
Hope this is of some (remote) use...
Steve Marshall
Group IT
Technical Support Supervisor
(aka General Meddler)
The Expro Group
Reading
UK