I am currently working on a hack of Fire Red, and I wanted to make a simple adjustment to Digglet's Cave. I changed the map's layouy slightly by adding another path to walk through. Just changing 1's to C's and arranging the tiles to look proper.
I had completed my edit, but afterwards Digglet's Cave and Viridian Forest became inaccessible. Upon entry the screen would turn black and freeze.
I've edited many of the other maps in the game already, completely overhauling some of them, and no errors like this had occurred, any idea why this happened or mistake I may have made?
Off the top of my head I would guess that it's some sort of data corruption involving the attributes in the maps' headers. That, or some bizarre oddity involving level scripts or warps.