My rhino would give me issues like this at one point but I found a method that works well for me. They are very intelligent animals so they respond well to kindness and starve for attention. Is he in a quiet room where he can be undisturbed? Usually it is as simple as them not liking something in the room and something scaring/stressing them out.
If you can get yours out, soak him in the bathtub if you have one and just keep an arm in there with him. It will usually relax them. Talking to them in a calm sweet voice can reassure them you aren't intending to harm them.
Here's a brief video on how I got mine to be dog tame:
http://www.youtube.com/watch?v=fMXoNTq2r_U