MuseScore 9.4 hangs in 5-line drum part

I posted the following text in the General Discussion Forum. iDave2 responded that "Hang=Bug", so I'm posting it again here. I hope this is the correct procedure. I couldn't tell that my mscz file was attached to the previous post, so I'll try it again here.

From the General Discussion Forum (see http://musescore.org/en/node/1746#comment-3866 )

I'm relatively new to MuseScore, but I've gotten proficient enough to write full scores for my septet. I've never been great with drum parts, but I'm trying to expand. I've just started the attached score and am trying to add the Hi-Hat Pedal to beats 2 and 4 in the first bar. I would suppose I should be using Voice 3 or 4, but they don't appear to be active within the bar. If I simply drop the Hi-Hat Pedal on beat 2 (Bass Drum turns red) using the mouse, MuseScore hangs and I have to get the Windows XP Task Manager to terminate MuseScore. I intentionally chose the 5-line drum part, hoping it would give me more flexibility for including multiple drum actions. I have an excellent midi device (Clavinova), but I do not have a PC connection to interact with MuseScore, other than exporting a midi file to a USB device. I've not been successful in trying to import a midi file into MuseScore. I don't know if this is a bug or a novice user problem. A Forum search didn't give me any ideas. Any suggestions?