后台线程如何挂起UI线程？

I am using a background thread to initialize an instrument over USB. The UI hangs when I try to open the device. I would expect the background thread to pause when calling Open on the device, but not the UI thread. I am testing this with no UI interaction from the background thread. I don't know how to debug the problem, and it's too broad a question, but perhaps someone has seen something like this before. There is nothing wrong with the ActiveX interop as far as I know, the device works correctly. This is the general approach:I am using a background thread to initialize an