When copying from an imaging document software which is abobe reader to a citrix environment. The user receives this error

There was an error while copying to the clipboard. An internal error occurred.

I cleaned out the temp folder and rebooted and un-installed abobe 7.0 twice and nothing is working. I think I read someone that it could be ntuser.dat file.
After receiving this error the user can work all day and not receive it again or until her temp folder gets full.
What's next

Is the Adobe Reader program installed on the local computer on within Citrix?
What are they trying to copy (text or graphics) and what app are they pasting it in?