Sorry for delay. I have now checked it all out.
My conclusion is I think you must have been using a different mame exe but the bug changed it.
MAMEUi does not work well updating the list. It is working but produces dialog boxes on the verify. You would have noticed it if you were using that exe.
For GameEx just use Vanilla mame.
If that does not work, please let me know.
Cheers.
Tom.