i was going to post the same thing.. I am getting this too, however there are two versions on my system that behave differently and maybe that will cast some light.
I initially had a bunch of roms from various places, and mostly 0.146.
they did not work with latest mame, however worked with mame32ui, so i made this the executable in mala.
everything works fine.
being a total noob, i was not sure why different versions had issues, however i then got v0.147 both mame and roms, and they all play nicely together.
however i have lots that friends play on the ones that were working, so i set up a new folder. I have mame0146 and mame0147 with separate executables, roms, mala installations, the lot.
mala in folder 1, everything that runs runs good.
in the folder 2, every time i exit a game i cannot use mala. it is NOT unresponsive, it is simply not focused, pressing alt+tab always goes to mala and makes it work, however i don't want an alt+tab button on my CP.
they are both set up the same, just 1 is using mame32ui and one is using mame0147. the rom rolders are different, however all other settings are the same.
i have also noted that there is a lot of stuttering of audio / video in the second installation and none in the first.
does that help to identify the problem?