Access 2003 Holding Shared locks on tables until exit

I am a Sql Server DBA who does not know Access at all, but my users are
complaining that when they run their Access application under Access 2003,
shared locks are held in Sql Server until they exit the application. The
same code run under Access 2000 does not hold these shared locks (for
example, running a simple select to populate a form). I am at my wits end! I
can see the locks with EM, but can not see why this is happening. Perhaps
Access 2003 has some kind of default setting of the Isolation Level, or plays
with the transactions themselves. Other people must be having this problem.
We use ODBC to gain access to Sql Server 2000 from Access.

Any suggestions?