I have the same problem with me, it starts when I open Premiere for the first time, after that AE always freezes on Media Core screen.
I have tried all the solutions qith QT32 server, if I remove QTserver32.exe from the folder after will work normally, but I can’t export to quicktime.
So I solve this (its not the best solution but solve it) opening Premiere befere starts after effects. If I do this AE will work normally.