Great article on investigating the deadlock. Just a note that if you're running SQL 2005/2008, the trace flag 1222 (http://msdn.microsoft.com/en-us/library/ms178104.aspx) provides a lot more information so you don't have to do quite a much undocumented digging (though I found it very interesting).

Instead of the trace flag, I'd personally recommend setting up WMI to log the deadlock info: http://technet.microsoft.com/en-us/library/ms186385(SQL.90).aspx.