I had this problem before. I recently dropped my ace mods and went total ace2. All I had left was visor. After removing visor this stopped happening with me. If you're running visor disable it and see if it helps.
You're right. Modifying the minimap cluster in any way with Visor causes it. :( Deleting Visor entries for the minimap returned map behavior to normal. Curious why this happens though?
Another black map issue, "/squeenix reload" doesn't help, but reloadui does. Each time I open the "big map" (not modified by addons) and then close it, the minimap seems to be behind artwork like the oSkin top and bottom frames, but also behind self-defined artwork frames. Maybe some issue with frame stratas?
I'm getting a similar issue, but it's not when opening/closing the world map. It seems that whenever I'm indoors my map blanks out. For instance in AQ40, the minimap is visible until passing Skeram and entering the actual temple, then blank for the entire interior. /squeenix reload and reloading the entire UI do nothing to fix this. Strata issue? Using latest off SVN.