Here is a possible temporary fix to play Metal Slug X with the new KBMAME if you get memory errors:
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It seems that some PCs can run it with only 64 Mb, while some can't even
with 96. Anyway, while I'm trying to figure out why it doesn't work on some
PCs, they can use the "properties trick".

1. Open a Dos box in Windowed (not full screen!) mode
2. Start up KBMAME
3. While the rom is loading, hit the properties icon on the dos box
4. Go to the Memory  tab (not required, though)
5. Close the properties tab (before the game finishes loading)

That should work for the time being.

- Deimos