I have this happen to me when my preferences became corrupted, so you might want to try deleting them upon start-up. If you're on a Mac, hold down the Command + Option + Shift keys as you start After Effects, this will allow you to delete the corrupt preference file. On a PC its Control + Alt + Shift.
Johnny Cuevas, Editor
"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.