Quicktime not opening AVI files in Lion.

Two must have system preferences: Flip4Mac and Perian. Those will cover most of your codec needs.

http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=9442

http://perian.org/

yes i have encountered its a stupid bug. is the avi file playable with quicklook? if yes then it is the stupid bug. if you can't view it with quicklook then try to reinstall perian. if you don't have it installed then download it. it supports every codeck you can think of

Click on the video in the Finder and 'Get Info'. What is listed for "Open with"?

divx might interfere with perian because perian already covers divx and xvid. Only one solution, not both..

simply uninstall every 3rd party codecs you have installed and go with just one if there are more then one to choose from.

Perian and WMV ( flip4mac ) is all I have on Lion and it plays everything, even downloaded youtube videos ( flvs ), the videos my Samsung mobile phone makes and the strange encoded avis that my sister sends me via email from her vista machine.

;-)

I have Perian installed, don't have DivX installed and when I try to open an .avi file it says that I have to use QuickTime 7. Is this right?

When you say third party codecs are you referring to programs such as DivX. I am having the same problem as the original guy. I only have DivX. Are you saying I should uninstall that and that there are other movie playing programs that are on the Mac already? Thanks

If you are using Perian then you should remove all extra (3rd party) codecs that it supports such as DivX. These codecs include:

FFusion, Xvid Delegate, 3ivX, DivX, DivX Decoder, XviD, msmpeg4v1, msmpeg4v2, AviImporter, EX_M4S2, Casio AVI Importer, AC3 Codec, and MatroskaQT.

I am not using Perian. The only third party program that I was using was DivX and even after I uninstalled DivX it still won't open the videos.

I would give Perian a try to see if that works.

Also, have you tried opening the video in QuickTime Player 7? If so, and if it works, get info on it from within the Player and list it Format specs.

What is the difference between QuickTime that is on the Mac originally and QuickTime Player 7? I'll try that Perian program. Thanks

So the solution is re-installing Perian? As I encountered the same problem after upgrading to Lion OS X

Using just Perian didn't work. So I don't know what the problem is because the files worked prior to downloading Lion