CPU jam in Super Mario Bros. The Lost Levels

[Crypto]

As I was playing Mario The Lost Levels, after I beat level 4-4 but before I entered level 5-1, the screen went completely black and in the left-hand corner it said "CPU jam". What does this mean? Is there any way I can fix it?

[Kong]

It's probably because it's a hack. Where you playing in Full Mode or Score Mode? If you play in a different mode, it might work better.

[Crypto]

It isn't a hack, it's an actual game:

Super Mario Bros.: The Lost Levels - Wikipedia, the free encyclopedia