Corruption with tied note in multi-voice

Slightly separate from related problem .

1. Create 4/4 piano score.
2. Enter semibreve in second voice.
3. Enter a same-note quaver in the second voice of the next bar.
4. Tie them.
5. Delete Voice 2 rests.
6. Select the quaver in the second bar.
7. Change to semibreve.

Expected result: Semibreve appears in bar 2.
Actual Result: Quaver and double-dotted minim tied (Workaround: Choose semibreve again). Quaver suddenly appears in bar 3 (score corrupt after bar 2).

Using MuseScore 1.0 and Mac 10.4.11. In 2.0 nightly build (4112), there's a crash (also see #8996: Not possible to change a value beyond bar in multi-voice).