COM+ idle shutdown inconsistency after moving from Win 200..

Working with our Wintel 3rd Party Support, we have noticed some
inconsistency with the COM+ Idle Shutdown functionality after moving
from Windows Advanced Server 2000 (IIS 5.0) to 2003 (IIS 6.0). Our
idle shutdown (Advanced app properties) setting has always been 5
minutes for the application, and 30 minutes for the session. This is
used to clean up any loose memory and database connections, and also to
roll over our log file names on a daily basis. Under 2000, it only
seemed to get 'stuck' maybe 3-4 times per year. When I say 'stuck' I
mean the application does not shutdown on idle even when not being used
for much longer than the idle setting. Under 2003, we are seeing it
almost consistently. I can verify in the app logs that there are
numerous 5 minute periods of inactivity. What we are also *sometimes*
seeing is that the idle shutdown is only occuring after the sum of the
IIS Application Pool session timeout setting of 30 minutes + the COM+
idle shutdown setting, which would be 35 minutes. We changed them to
other values and confirmed that this is the case. What settings would
cause this association?

The real problem with this is that without an idle shutdown over
several weeks, we are seeing hundreds of idle database connections
sitting around, and eventually SQL Server throws our application
CDBExceptions causing everything to come to a halt. We're
investigating if and where the application is leaving DB connections
open. SQL Server is set to unlimited connections, and to recycle them
when needed.

I know there are a lot of settings and other information that might
help in debugging this issue, let me know which ones are relevant and I
will post them. Thanks!