Problem with playing certain mp4's in Quicktime Player X

Today I updated my System to OS X 10.6.3, which included a Quicktime update

After updating I can't play certain mp4 movies anymore with my Quicktime X Player: I can hear audio but I don't see video.

What is so strange about it that until today I was able to view them without any problems.

I still can watch them with VLC player.

When I click on file info, I see these codecs: AAC, H.264, MPEG-4 SDSM, MPEG-4 ODSM

How can I solve this problem? I am using OS X 10.6