Make sure it includes the latest version of Text Will be Text (
http://www.bay12forums.com/smf/index.php?topic=138754.0)
Also, check your init.txt file. Make sure FONT and FULLFONT are curses_1280x600.png, GRAPHICS_FONT and GRAPHICS_FULLFONT are gemset_map.png, and PRINT_MODE is TWBT
If it is missing TWBT, the installation doesn't contain folders, so here's where to put each item:
realcolors.lua goes in ./hack/lua
The contents of 0.42.05-alpha1 go in ./hack/plugins (note: the
contents of the folder go in here, not the folder itself)
You can ignore the rest of the files, as GemSet already has its own version that you don't want to overwrite.