SQL Server 2005 Blocking Issue
The easiest way I look at it is, right click on the database in SSMS and under Reports => Standard Reports => All Blocking Transactions. There are other standard reports with blocking transactions as well but I found all one pretty useful.

The other thing you could do is setup a SQL Server Agent Alert for figuring our locks for your database. 

Type: SQL server performance condition alert
Object: SQL Server:Locks
Counter: Anything you want
Instance: Database
Rises above: {x} number of occurrences you want to look for.

And have the alert set to email you when the condition is met (considering you have Database Mail setup already).