[dba-SQLServer] Processes Causing Blockages SQL 2000

I have 10-12 Access 2k front-end applications against a SQL 2000
database.  There are about 70 users total.  Occaisionally, including
right now, they perform otherwise normal stuff that randomly causes
"blocking" on the server.  No one else can do anything when this
happens.  Make the offenders logout and re-boot, problem goes away for
2-3 weeks.  The thing that puzzles me the most is that it is always
"unbound" operations that do this (ADO commands and pass-thru queries),
never any of the bound forms.

I believe it may be latency on the network, but their admins insist that
couldn't be the case. 
Any advice?

TIA
Steve