OK, I have a nice MAME cocktail cabinet which I purchased from heinekenlvr around Christmas. It was working great and all of a sudden none of the games will run. It is running Mame, Windows 98 and has ArcadeOS as the front-end. Now when I select a game to run it appears to be loading except it goes to a black screen and never displays anything.

It was working fine until I left my son alone with it (he is six). I am not sure if he changed one of the settings in the configuration by accident or not. Windows and everything else runs fine.

Not sure if this might help but: If you tab into Windows from the "black Screen" and tab back you have a very small blue grid which gets displayed in the centre of the screen.

Does anyone know what I should try? Please help as this is driving me crazy.

I think we'd need more info to help but lets try but I'm not very familiar with arcadeOS.  Do you know if you have a mame32 version of the emulator on there, or if I assume with arcadeos, you're running either the dos version or a command line version?  Take a look in the directory of mame and see if you do have a mame32 version and if so, run it and see if you can run your roms through it.  If you don't, I recommend you get it to try and see if at least your rom set is ok (though I can't see how it wouldn't be).  Anyway, this will help determine if its just a configuration problem with your arcadeos/mame combo.

Also back to your ArcadeOS setup, after starting a game and you have the black screen, wait about 10 seconds or so, then insert a coin. When you do, do you hear the sound effect of the coin inserted?