I just reinstalled Blender 2.63. Previous to that I saved my theme .blt file, which was made in 2.63. I reinstalled and enabled Theme Manager, put the .blt file in ~/.blender/2.63/scripts/presets/theme, and tried loading the theme. I got an Installation Failed error. Then I tried instead loading the theme from somewhere other than ~/.blender/2.63/scripts/presets/theme, and got “Installation succeeded, but theme could not be read”
I get very tired of having to re-set all my theme options every time I reinstall blender. This time, I created the theme in the same version I’m trying to install it to, so there’s no reason it shouldn’t work.