The modpack won't let you use any map mod BUT Opis. it re-creates the .disabled file while leaving the Undisabled file intact. This happens with Journeymap, Rei's Minimap, and Zan's Minimap. if you try to disable Opis, it re-enables while leaving the Disabled file intact, creating a new file (this happens with all the other mods. this is version 1.0.7 that I'm using, not sure if this matter has been fixed as of yet.
EDIT* On a completely different tangent, of the same problem kind of, Opis Minimap won't keep the Waypoints on SMP Servers, at least that's what happened with mine.