This is an issue that some people have run into when using one of the newer versions of UWUVCI (3.99.0), the latest version should resolve this problem.
A tl;dr: as to what happened, basically one of the tools that were being downloaded didn't finish downloading before the program started up because of this a bad inject was made.
Hey, I wanted to reply in regards of the help you've lent me on this, and this is an update on the game so far.
Fighting Fantasy: The Warlock of Firetop Mountain boots up now, and you're allowed to navigate the title screen.
The first game that was used wasn't injected well (I think I used Warioware touched), and it crashed as soon as you got into gameplay portion of it after turning at the first dock to face the island.
When I attempted a different game, I used Mario Kart DS US and it seemed to work pretty fine so far. It doesn't crash anymore when playing and I've made a good portion of the game yet without any game breaking glitches or bugs. If you are into RPGs, this is one to play. It's an 1st Person Action RPG, and it plays really amazingly. It's a puzzle game, too, because if you're navigating areas for the first time, you will be puzzled occasionally to where you have to find clues in rooms you previously explored, and the enemies get more unique.
If you would ever like the inject, just send me a message, and let me know how it goes. Cheers bud