There seems to be an issue with the custom MIDI soundfont support in 1.6.
If I'm using a custom soundfont, the first file you try to play works fine but anything after that it get's stuck in an infinite loop inside of load_soundfont() with "Loading..." on the screen. The only way to fix it is killing the app.
I tried looking into this a bit yesterday, but haven't yet figured out the cause. It appears that the first file it tries to look for is "C:/timidity/timidity.cfg", and it freezes around that point. The problem may be internal to timidity, but perhaps something isn't being cleaned up properly on the outside?
Have you been able to reproduce this problem? I'll look into it some more the next time I have time, but I thought I'd report it in case the solution is obvious. (I looked around the timidity code for awhile to try and figure out where it was deriving the C:/ path from, but didn't find it before I ran out of time to look. I'll be looking for that the next time I try to figure this out.)