Thanks for your answers and your time, Dave!
There is a inconsistency with my AE, I have CS3: Some time ago I made a project in which I have a .mov video (size: 720×480, Format:Quicktime, 30fps,22Mbps,Codec:MPEG-4V(Family:)) that works fine and the AE does not crash. But When I try to make a project importing another .mov video ( size: 900×600, Format:Quicktime, 30fps,12Mbps, Codec:MPEG-4(Family:)) or indeed the same I use in the old project the AE crashes when I try to add it to the comp timeline.
Now after reading your post I use quicktime pro to encode this videos to Animation, Million of colors, High Quality, current size, but in the moment I try to add them to the timeline AE still crashes.
All these QT files where made in the same AE.
Dave, hope you could help me.
Thanks a lot,
M