1. Make sure the file name matches the one in the CFG file; it's case-sensitive.
0901.igb != 0901.IGB
2. Make sure there is an empty line at the end of the CFG entry.
<empty line here>
3. For importing BMP/DDS files, make sure the CFG entry for that particular file does NOT have a dash "-" in front of DXT1(or 3 or 5). SkinnerUI crashes every time I include that dash when importing files, but it's fine for exports. @_@ So, you must reverse the color channels from RGB to BGR before importing, just like that blue Carnage pic I provided in the tutorial.
If you still have problems, then you can ask for help in that guide. Good luck.