>Ok, I see. Let me check that. That's probably what causes this. I also got that one one more time today and the traffic was low. So, it is certainly related to another hit that is affecting this. I will let you know.

It's not a simple tasks to avoid deadlocks sometimes. You should read more on deadlocks, what causes them and how to avoid them.
In general, the most common cause of deadlock is when statement 1 locks table A and than B and Statement 2 locks table B and Then A. It's simplified example but may give you an idea where to look.