I have been using Gimp for about 5 years and have never had this problem before, and its extremely frustrating. Below is a picture of the actual error since it is difficult to describe, but basically when I load Gimp the text that would be there for every command box is showing up as a square character.
My only guess for fixing the problem was to try to uninstall and reinstall Gimp. I've done this twice with no success. It seems that the program is having difficulty accessing the necessary font to run the program, and I cannot figure out a way to edit or redirect it.
As a side note, my system files fonts were uninstalled about a month ago and I had a similar error with my entire computer being composed of symbol characters instead of letter characters. I solved this by reinstalling the system font files, but ever since Gimp has not worked correctly. I'm really quite at a loss as to how to solve this, and uninstalling does nothing to solve the problem.
I looked on the Gimp website for more information on how the fonts work, and apparently it runs with fontconfig, so that is my only guess as to what is wrong, but I know nothing about fontconfig or why it would keep messing up like this if I haven't touched it since I installed 2.6.