I had this same problem and found it to be a problem that only presented when trying to install the maps while playing the game from a "streaming" installation. In other words, if you are playing the game without it being completely installed, but instead opted to play while it is streaming to your computer, then the problem lies in the fact that the maps installer cannot complete its installation because there is no everquest2.exe until the streaming is complete. ugh!!!!! I can't tell you how many times I uninstalled the maps and reinstalled them and how many ini files I created and placed in the ui folder and in the everquest directory and everywhere else I thought it might do some good....., and then I started looking for the file it was asking for and abra kadabra... there it wasn't.
so I downloaded the whole game when I wasn't playing the game, reinstalled the maps in the new game folder and when I loaded from the new game folder, eq2maps worked just fine. eureka!!
