Use the dynamic management views to gather better information. Sys.dm_exec_requests will show you the processes. That will let you more easily see what the query is of the blocking process:

SELECT * FROM sys.dm_exec_requests AS der

CROSS APPLY sys.dm_exec_sql_text(der.sql_handle) AS dest;

Just add a WHERE clause for the process id. sp_who2 is a very old school way to look at servers and their status. I strongly recommend you take a look at this book.