I know exactly what is going on (since I put together a new English demo that is smaller).
The Melty Blood patch only works with the full retail version. We created a new demo based on the Trial 3 demo, which is smaller in size (many files inside of the demo are not compressed as they should be). What is happening is this:
You have Data00.p and Data03.p in the demo, and our patch is adding Data04.p and replacing the EXE.
Data04.p contains a new default character selection file, so you can probably see all of the characters in the selection menu, and all of the stages.. but the problem is, not all of the files are actually in the demo (except the stage files, but your not supposed to be using those), hence why you are crashing.
As painful as this might sound, the best solution is to download our trial demo.. it will also save you some space.