There is a process that bulk inserts data into a sql table from 3 sources in parallel. After adding a primary key to this table, 2 of the bulk insert queries get cancelled after a while due to being the victim of a deadlock. This never happened until I added the primary key. I assume the problem has something to do with the clustered index that was created by adding the primary key.
For now I'm just going to remove the primary key and then create a non-clustered index on the table. I would like some more info on whether the problem is what I think it is, and if there is a way for me to add a clustered index without screwing the load process up.
Not sure if it is more poison than a cure, but Robert offered to drop the clustered index before a huge bulk insert:
http://www.simple-talk.com/sql/learn-sql-server/bulk-inserts-via-tsql-in-sql-server/
We just lock the table and minimally log transactions.