One method to troubleshoot SQL Server Deadlocks is to use the SQL Profiler.
In SQL Profiler, in a new trace, select the Events Selection tab and expand Locks:
Select the Deadlock graph:
Run the code that causes a deadlock. In profiler, you will now see a line for the Deadlock graph. Selecting it will show the graph with the process that succeeded and did not succeed:
Hovering over the graph shows the SQL trying to be executed: