I´ve discovered something interesting while playing Puzzle Time (pzletime) in MAME.
Black screen, except for this: E2-ROM ERROR
It appears that, unless you already have "credit/-s inserted" you must remove the nvram-file from its folder if you want to play...
In other words: if you "start it up" and inserts a few extra credit or two you will be able to play the game next time without interference...
The version I´m using is: MAMEUI 32-bits, version 0.140
Is it a "temporary bug" or something else?