Go into the Customs Database and download the 'Other Files' for either Rush - Far Cry or Taco - Puttin' on the Ritz.
Both of those are mine. In the Other Files I provided a "second version" of the released song for people that wanted to play it. The download for each is a .zip file which has instructions for patching a con file (since that's what you have to do for mine). Just replace the names for everything with what you are working on, and that should tell you everything you need to do.
If you still have a freezing issue after, you might have altered something on accident in the .mid when exporting. If so, post the mid somewhere online to download and someone can try and take a look.