I just discovered a bug in 1.9.3 released yesterday. The new text highlighting feature introduced a situation that could occasionally cause Digital Fake Book to become unresponsive when a button was clicked.
Sorry about that. Programmers make the worst testers of our own software. If anyone wants to volunteer as a beta tester for the next release, please let me know.
1.9.4 can be downloaded from the Digital Fake Book page.