I installed some codecs, itunes will now not open.

Yesterday I installed the Ace Mega Codecs pack. During installation, it removed Divx and ffdshow. I believe it did something to quicktime too, because itunes refuses to open now; whenever I try to open, I get "itunes has encountered a problem and needs to close". I had to remove the codec pack mannualy, as it would not uninstall in the regular way. Have tried repairing, reinstalling, and uninstalling and installing itunes and quicktime again. iTunes still refuses to open.

I believe the problem is with quicktime, as when I first tried to reinstall iTUnes, that's where installation would stop. It's already out of safe mode, so that's not the problem. Yeah I tried the standard apple solutions- a no go. Have also scanned computer with ad aware and norton anti virus. Not the problem.

Any help would be very much appreciated.