Is it necessary to close Excel, or can the user do it?
When running Excel through automation from VB 6, I've had problems when the outside application STARTS Excel and then releases it instead of closing it.
Specifically, VB opens Excel, does some stuff and then closes itself while leaving Excel open. User closes Excel at a later time and an error sometimes results with an obscure message (sorry - don't remember the message).
After some research, it was related to one of those "memory leaks" and the solution was to require the user to open Excel first, and then connect to it using GetObject instead of Opening it using CreateObject or the method you used.