What exact version of After Effects? What exactly happens when you try to run After Effects?
My AE is getting error too,
Last log message was: <140735269139200> <AppDirs> <5> Required Dir = /Applications/Adobe After Effects CS6/Adobe After Effects CS6.app/Contents/Required
Generating crash log, which may take a few minutes
What exact version of After Effects are you using?
If you're on CS6, but not on 11.0.4, you need to update
If it still doesn't work after that, try this: fixing permissions problem that impedes start of Adobe applications
If you haven't updated AE CS6 lately, do so. There's a fix for AE for Yosemite.