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OK, it hasn't been reported as an actual bug, but similar issues have been reported in other threads:

http://xenforo.com/community/threads/page-doesnt-display-properly-when-trying-to-edit-posts-with-attachments.15553/

http://xenforo.com/community/threads/random-white-page-errors.15444/

I actually encountered it myself last week and Mike did some checking and suggested it is either a JS issue or a Chrome bug.