Sorry, thought you meant the map window didn't appear, not that it appears but no map content.
I assume you've restarted and done complete file check, so if still not working after that, I'd delete the EQGraphicsDX9.dll file fromt he main everquest directory and do full scan to replace it.
If that doesn't work, I'd check a few other things, like run the DX diagnositc text and check your video driver is working correctly, if either appears to not be functioning correctly, I'd try re-installing the same version video driver again, and directx9c as well.
Seems that a corrupted DX file is the most common for a persistent problem. I don't remember having this specific problem being persistent, but wife's computer often inverts the maps, or displays only partial content, and is generally fixed by restarting (and sometimes requiring a brief cool down, depending on the time of year).
You might also try creating some maps using the in-game map tools and see they show up. And if they do, make sure the file you created is in the correct map directory (Use layer 3 as the active layer, and file should be zone_3.txt) and will have some content in it. Mapfiend doesn't use *_3.txt layers in general, and if it does, they're empty, so you'll know if you edited it or not.
If you can create a map and exit the game and log back in and still see it, then its problem is either a configuration problem on where EQ is storing the maps, or the downloaded maps are corrupted (although, you should be able to see the default zones, like PoK without downloading any maps, as EQ gives you the base for all the city zones).
Maybe this will be more helpful in finding the root of the problem.
Yther Ore.