This is fixed in After Effects CC (12.0), and we're working on a fix for After Effects CS6 (11.0).
It's because Apple changed some OpenGL bits in recent versions of the operating system.
Do you know if there will be a fix for AE 5.5?
Will you be sending out a software upgrade notice when the fix for AE CS6 is completed? Any sense of how long it will take to finish the fix?
It is highly unlikely that there will be any future bug-fix updates for After Effects CS5.5.
We are targeting release of a bug-fix update for After Effects CS6 within a couple of months.
Current updates are always listed here: http://adobe.ly/lsrkmJ
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