OLEDB Connection Pooling issue (Oracle9 Client, 10db)

[Danimal1000]

Greetings:

I'm involved in migrating an existing COM app (uses VB6, O8 Client, connecting to Oracle7 DB), to a new environment.
Our new environment will use the same code (hopefully), and Oracle9 client connecting to an Oracle10 instance.

The existing production app has no issues with connection pooling, typically running between 5 and 8 db connections to service about 1000 clients.
However, the new environment is not pooling correctly, and new connections keep getting opened.
Can someone point me to any known differences between the O8Client/O7DB connections and the O9Client/O10DB config?
I've googled every aspect of this, from MTS, COM, OLEDB, Oracle Metalink searches, but haven't found much help.

Any assistance is much appreciated!