Time Sig not laid out correctly after some changes

Context: commit 372f990 (2013-03-16)

Steps:
1) Create a new score with time sig 4/4.
2) Change 4/4 into C using the time sig contextual menu.
3) Revert to 4/4 either by undo or by using the contextual menu again.

Result: the 4/4 time sig is shown with the two 4's misaligned.

This is not the only case, just one easy to reproduce.