No instruments in instruments window

Hi all --

I have musescore 2.0.1 3c7a69d, installed from RPM on Fedora linux. My problem is that instruments show up in some places but not in others. In particular, in my Instruments window (for example, if I open a score and press 'i'), there are no instruments. There is a combobox that says "All Instruments", but nothing in the left-hand list, and no other choices in the combobox.

However, instruments are around. If I open a score that already has instruments defined, they play back properly. If I do File->New... and try to do Choose Instruments, I can't do anything. But if I choose a preset, such as brass quartet, the score works fine. But I have no way to change any of the instruments after the fact.

In the mixer, I do have access to lots of sound font instruments, so I can make the Tuba play with a Trombone sound.

I have checked that /usr/share/mscore-2.0/instruments/instruments.xml exists and has > 500 instruments defined. I tried installing a new soundfont, GeneralUser GS 1.442 MuseScore, but still the Instruments window is empty.

Any ideas?

Thanks,
Bob