Generally speaking, you should provide far more information about your setup, the way AHMI is used and screenshots of the error itself.
I don't have a solution for you but only a few questions:
Have you contacted NComputing support to inquire about this or similar issues?
If the AHMI application starts and runs for several operations, could it be that it is just unable to gain access to .Net Framework afterwards?
For troubleshooting purposes, have you tried running the AHMI on the machine itself instead of on the thin-client?
Hopefully, some other members might provide some clues as per their knowledge.