Use the -ot option in your command line.
This often happens when an object that isn't thread safe is called. Some ActiveX components will not run multithreaded, possibly because they're not thread safe, and the only thing you can do is to run it with the -ot option.
This -ot command line option does NOT make the engine run on a single thread. It forces the CoInitializeEx call to set the threading mode as SINGLE-THREAD-APARTMENT. This simply means that each COM object you invoke will be isolated from other threads.