When two stored
procedures get into a deadlock situation, sql server makes a guess
and kills the one it deems less important.
The immediate resolution
is to rerun the stored procedure manually. The long term resolution is identifying the cause and reengineering queries, changing database setting, changing indexes or improving the hardware platform.
SQL Server technical bulletin - How to resolve a deadlock
Visual deadlock graphs:
Analyzing Deadlocks with SQL Server Profiler