Safari won't play some videos

[fscarpa]

I'm having some troubles here. Youtube videos work fine. But if I try to watch Apple tutorial videos, they won't run on Safari (5.0.5). They run with no problem on Firefox. I've uninstalled Divx, Perian, Flip4Mac but it still won't work. All I get is the audio and the spinning fan, but no image. Before uninstalling DivX I hadn't even that - all I was getting was some error message (DivX couldn't show the video, or something like that).
If I switch Safari to open in 32bit mode, I can get both audio and video, but it's weird: it plays like a YouTube video, with the controls on the bottom (same Youtube format) AND the quicktime-style controls a little bit higher, still on the bottom, BOTH not accessible (picture).
What shall I do?

 

[satcomer]

Do you have the Safari add-on AddBlock installed? Sometime it blocks Apple videos. You have to click on the hand icon in Safari's menu bar and add the apple domain to the exclude lists.

 

[fscarpa]

No, I don't have AddBlock installed...

 

[fscarpa]

I even tried this:

https://forums.macrumors.com/threads/372124/

...without any success at all!

 

[motulist]

If uninstalling DIVX improved the problem, then that makes me think that the problem was definitely caused by installing DIVX (or some other similar codec extension). Perhaps there are still some other DIVX files floating around your system that you still need to remove, or perhaps there are some additional code you added that also need to be removed.

 

[fscarpa]

Well, I've removed every internet plugin, perian, flip4mac, divx and so on... Even removed quicktime plugin, but then when I tried to play Apple tutorial videos I got the "missing plugin" message.
I even removed Safari and reinstalled it next, but the issue remains.