Alt-shortcuts (for typing intervals above a note) don't work on Mac

I'm on Mac OS X 10.8.4 (Mountain Lion), and whenever I try to use alt-2, alt-5, or alt-8 to type a second, a fifth, or an octave above the selected note, nothing happens. Using the alt key works fine for the other intervals (1, 3, 4, 6, 7), however. I don't have any conflicting keyboard shortcuts so far as I know, especially since nothing happens when I try those three.

This only started happening when I upgraded to 1.3, revision 5702. Somebody else had a similar issue back in September, albeit on a tech preview of 2.0: http://musescore.org/en/node/18203

Any ideas on how I can solve this problem? I don't want to have to downgrade. Thanks!