I suffered this problem too, and it's because of two bug fixes after I dig it awhile.
bug#11484: 23.4; Scrolling leaves traces of old text behind
LCD-smoothing was turned off to fix this bug,
and
bug#11541: - Another reproduction - Emacs 24.2; Null pointer on OSX with
I simply revert these two fixes, and problem you mentioned is gone.
So, maybe there are more deeper things around of these two bugs.