Also I just fired up MAMEUI .241 and played around a bit (I use IV/Play and baseline MAME normally). And I saw that MAMEUI did again create a mame.ini in the \ini directory even when I had one already from baseline in the root directory. So make sure you don't have two accidentally. I guess you could standardize on the one in the \ini directory for MAMEUI.
I suppose another thing you could try is getting that old version of MAMEUI that worked and set it up in a fresh directory and see if it produces better results and then layer the latest dist package over it.