@Richard.
if you can reproduce those hangs, it might help if you could create, zip and upload a madVR debug log for me to look at. If it's a bug in madVR, the log might help me figuring out where the hang comes from. However, if the whole MC hangs, I'm not sure if that can be the fault of madVR, since MC runs madVR in its own thread, so MC's GUI should stay active, even if madVR itself hangs. @Yaobing, what is your opinion on this?
The problem with the "old frames from the windowed buffer" is a known problem, but I'm pretty sure it's not a bug in madVR, but rather caused by the Windows GUI ("Aero"). I'm not sure if I can do anything about it, I kinda doubt it. You could try disabling Aero/Desktop Composition, maybe that fixes the problem. Or you could disable the exclusive mode, if windowed mode works well enough on its own. Or you could try to avoid switching between windowed <-> exclusive mode, if you can.