Do you have any initialization logic in background thread? Do you call office API in background thread? Or any other threads? Does any code calling COM objects run in finalizers? Are there other add-in running on user machine?
Actually I may point articles about COM/RPC/STA/marshaling/threading which I used to learn root causes of such errors.
Actually I may point articles about COM/RPC/STA/marshaling/threading which I used to learn root causes of such errors.