DCOM client registration

[Jay Smilax]

Hello,
I am running into a wierd situation withthe DCOM registration.
We have an old DCOM component say, dcomserver.dll (This is developed
early 2000)
It is registered under COM+ on a windows 2003 server.
This is accessed from another windows application running on a clinet
machine.
According to my knowledge, the proxy( tlb) should be registered on the
client machine.
So, in the lab environment, I register the dcomserver.tlb on the
client, and everything works as expected.
If I do unregister the TLB, the application throws a "unable to create
an instance of the IDcomInterface".
(The client uses the CoCreateInstanceEx() and specifies the server
name where the DCOM object needs to be instantiated).

In the production environment, there is no clinet side registration of
the dcomserver.tlb.
And suprisingly, everything seems to be working fine in production.

I am modifying the old DCOM component and I need to install the
updated component.
I just want to make sure that I am not breaking the existing
clients(1000+) that use this DCOM server.

what could possibly be different between the production and lab
environment related to accessing the DCOM?
Is the client registration needed to access DCOM?
if it is required, how is it working in the production?
if it is not required, how can I get it to work in the lab?

Any help is greatly appreciated.
Let me know if you need more information.