I would suggest looking for help in the form of therapy. If he can do it alone, then their is not a physical problem so this may be a form of performance anxiety or it could stem from some sort of trauma from when he was a child. A therapist may be able to help in finding out what is causing the issue and provide a solution.
Good luck Kitkate...

ps, It's good to see you posting again...

__________________
Put me on wheels and I'll turn tricks.

Clever? Nah, I ran out of that years ago. But if you find this, let me know, k?
"The road goes ever on..." ~ Tolkien

In memory of my friend skip...
Go then, there are other worlds than these