Deadlocks aren't necessarily due to performance. You can have the fastest performing system in the world and still have deadlocks. Poorly written applications can cause quite a few. See the post below and it might help narrow down your culprit.

http://richardlees.blogspot.com/2011/11/causing-deadlock-in-sql-server.html

older but still good:

http://www.sql-server-performance.com/2006/deadlocks/