cannot enter two voices on the same staff

I'm attaching a score which demonstrates this issue. If you take a look at measure 48, click on the quarter rest in the bass clef, and try to click on the 2 (second voice) you see that musescore refuses to go into the mode where the 2nd voice is enterable.

I created this in a previous nightly build where it exhibited the same issue. Then I downloaded the most recent version b4e6343 which it also exhibits the same issue.
MuseScoreNightly-2014-05-24-1708-b4e6343.dmg