[1.0-pre1] Transpose by Key sometimes doesn't work correctly

This bug is frustrating me so much right now (in the sense that I can't find the exact steps).
It has been referenced in a few other threads (such as nodes http://musescore.org/en/node/3096 and http://musescore.org/en/node/8239), but those were more based on questions the person had, rather than trying to report the bug.
So... here we are... working in 1.0-pre1... Mac 10.6.6

Basically, when transposing by key... SOMETIMES it doesn't work correctly.
The basics of what I'm doing:
1. New score for voice in C in 4/4
2. Press 'C' 16 times for 4 full measures of quarter notes
3. Add a key signature on the third measure
4. Select the third, or the third and fourth measures
5. Notes --> Transpose:
Transpose by key, closest, choose a different key, transpose key signatures, click OK

Result: Always changes notes correctly. SOMETIMES changes key signatures correctly, but sometimes changes key signature in measure 3 and in measure 1 (which shouldn't be changing in the first place) incorrectly.

The crazy thing is, I can do seemingly the same thing a bunch of times, and get different results.
Clicking on measure 3 so the whole measure is highlighted... transpose... success
Undo, Unselecting everything...
Clicking on measure 3 so the whole measure is highlighted... transpose (to the same key as before)... FAIL!
repeat last two lines... success...
repeat... success...
repeat... fail...

What in the world is going on here...