RCW and CCW

Here is an OK intro: http://vbfaqs.blogspot.com/2008/06/overview-rcw-and-ccw.html

RCW is Runtime Callable Wripper. It is used by .NET to call COM objects.

CCW is COM callable wrapper. Used by COM to call .NET objects.

I am seeing the following error calling COM from .NET:

RaceOnRCWCleanup was detected.

An attempt has been made to free an RCW that is in use. The RCW is in use on the active thread or another thread. Attempting to free and in-use RCW can cause corruption or data loss.