I've had a problem with presets showing up as yellow and back...If that's the case, open them with GIMP or a similar editing software and make sure the files are scaled 512x512 and that there's nothing wrong with the .material file.
If you /can/ see the preset in preset maker, and it just won't export, you might have a problem with a)there's already a preset in the slot you're using, or at least the game thinks there is. I've had that issue with the first two slots. Or, b) you have no more room for presets, like you've already used all 12.
If neither of those is the case, I'm not quite sure what the problem could be...that's all the info I know on preset troubles. I used to have lots of trouble with presets, but once I re-installed it worked fine.