happens to me too when i import image sequences of ~1000 files.
however ae isn’t exactly “crashing”, i’d say. it’s not like you get an error message or anything. the whole process just disappears from one moment to the other. i find this a little amusing considering the minutes it can take to properly shut ae down when you’ve worked for quite a while.
usually, the problem occurs to me the moment i want to rename the image sequence (ae7pro here). sometimes just moving the mouse inside the project window is enough though.