Try a different alert, I'll be honest I have been lucky enough not to come across any deadlocks in SQL Server 2005 databases I've supported - things have been looking up, the deadlock event was set up and taken from a SQL Server 2000 script.
/****** Object: Alert [Deadlock] Script Date: 06/12/2008 17:46:22 ******/
EXEC msdb.dbo.sp_add_alert @name=N'Deadlock',
@performance_condition=N'SQLServer:Locks|Number of Deadlocks/sec|Database|>|1',
Facts are stubborn things, but statistics are more pliable - Mark Twain