Excel crash caused by AddIn UDF

Question

I'm facing a problem where I have a managed Excel AddIn which implements a AutomationServer (UDFs) and also the interface IDTExtensibility2. The AddIn uses a native COM Shim written in C++. Everything works like I expect, when the seperate client is running. If the client is not available, whenever the user starts typing a Excel function name, after the first letter, Excel crashes. If our AutomationServer is not loaded, this does not happen. I don't get it why the crash occurs because the functions are not even executed at this stage.

What may be the cause of this behavior?

Answer 1

Thanks to Simon Mourier's idea, I caught all exceptions when debugging and found after some research that an ExcelApp.CalculateFull() in the OnConnection-event was messing things up. See also http://support.microsoft.com/kb/284876/en-us which gave me the final clue to solve things.