So I'm running Morrowind Overhaul 3.0 mod and not much else really and haven't had many problems. Now all of a sudden I'm having a weird map problem though. Hoping someone can help.

I've had my map set up so that the top half of my menu screen is my map - stretched out to take the entire space of my screen (top half as I said). Up until tonight the local map always filled the entire space of the stretched out map, but all of a sudden I now have a black border on the right side about 4 inches wide in order to make the local map appear squished a bit to the left. It seems like it's just not scaling correctly no matter how I stretch the map as it will put black borders on either side to keep it more square instead of stretching the image fully like it used to be.

My regular game is still playing fine in widescreen and stretched accordingly. But it's just the local map that is now putting black borders on the side and not stretching correctly. Anyone have any ideas of what could have happened? It's the same way in all my saved games and a new game as well so it isn't a saved game bug. It just started happening about an hour ago out of nowhere.

The Morrowind Code Patch, which is included in the MSGO compilation, has an option to change the scale of the map so it can fit the Tamriel Rebuilt worldspace onto it. If you've selected the option but aren't running the TR expansion, you might have a lot of empty or undefined space, depending on where you are at the moment and how far the map can extend. With the map blown up to full width, it might do what you're seeing, but I've never tried that combination. If you recently travelled to a different portion of the island, and now it's showing an area which was previously off the map, it might explain the sudden change.

If that's not the case, then ignore me for making wild and wrong speculations.

The Code Patch also allows you to zoom in/out with the PgUp and PgDn (Page Up & Page Down) buttons.
Perhaps you just need to zoom back to the original scale.