You can enable traceflag 1222 and SQL will write the deadlock graph into the error log. That will help you locate the cause of the deadlock.
The only way to get a deadlock with select statements is if one or more is running with either the xlock or updlock hints, forcing an exclusive lock instead of shared as is default.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability