Contention is killing me

Hi all,

I have a single server that houses my Biztalk 2004 installation with SQL 2000.  I've never had a contention issue before until this week.  

I may have up to 10-15 individual orchestrations (unfortunately, all sequential convoys..business requirement) running simultaneously managing their own messages and everything used to run very well, nice and fast with no real backlog.  This week, however, when I receive a large amount of data for one subscription to fire off, all other unrelated orchestrations all of a sudden take a back seat to this one and I have seen a number of queue messages sit in a dehydrated state for hours until they start running again.  Before, I would see all of them running in the active state and all my messages would run fine without slowing down the other processes.

Any ideas jump out at what I can to to help this, without throwing hardware at it?  Hardware just is not an option.

Thanks,
-Rich