To understand why a SELECT statement is slow, you need to look at the execution plan to understand how the optimizer is resolving the query. Also, you need to look to the system to see if you are experiencing blocking or resource contention.
Based on what you've posted, that's all I've got.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning