Hey, i'm having a problem with my AE where every time i load it it hangs on 'initializing mediacore' for 4 minutes and then when it finally loads up it pops up with a box saying that i don't have quicktime installed. I am fairly certain that AE is not blocked in my firewall but i did find a temporary solution. i use AVG anti virus and if i temporarily disable it and load AE the problem is gone and After Effects loads up perfectly and doesn't display the quicktime error.
It seems that AVG pushed an update recently that caused an issue because there have been a sudden rash of people with the exact issue on the forums for the past day or two.
According to stuarts52800770 in this thread: In AVG Internet Security switch on Firewall, Computer, Identity, and Email options and AE launches and runs all fine. But switch on either of the Web options (LinkScanner or Online Shield) and it goes back to the QuickTime error and takes ages to start.