Hi, I think I found a serious Bug in Render.
I use 2.49b, and I heard the problem is visible in 2.50 too,
but I can’t certify that.
The file is very very simple, 1 Camera, 1 Mesh Plane, IPO to resize the Plane.
Bug : the Plane is cut in 2 parts on some Frame.
Please test yourself and tell me what’s going on.
It takes you less as one minute from your time
Render : (the gray Plane is in fact not in two pieces like it seems)
seems like you have a corrupt blend file
I dont think so,
I can do the same again with a new empty default file,
and making the same scene from scratch.
Just subdivide your plane once and the problem goes away. The issue is not a bug imo but a fairly common occurence in 3D rendering situations, where a single quad face is made to occupy too large an area, and the camera is relatively close the face – backing the camera off also fixes the issue.
A general rule of thumb is that when a single quad face more than fills the camera frustrum, it can cause glitches like this, so it’s always better to subdivide (even once) rather than use a single face for the entire plane.
OK, thank you for the answer, I learn something once again.
Someone gave me another trick : rotate the camera 360 on the Z axis.
It seems to work, and with it I solved my problem without having to change
my Meshes (in my original file they are more than just one, with UV texture,
so it was unconfortable to subdivide every of them).
… and just because my english is not good enough : what is “a bug imo” ?
imo = in my opinion
Cannot open your blend at the moment to test, and have never seen any issues like you describe.
In case it’s a graphic problem, whay operating system and grpahics card do you have.
I think OS and graphic card are not in the probleme.
People from the french BlenderClan have tested and observed the same problem.
I have tryied on 2 PCs, both with Win XP, one with Nvidia (???) and one with “on board” graphic card.
Sorry about the webspeak, bit of a habit. Rotating the camera 360 on Z is an interesting fix, I wonder why it works? Good to know, though.
If the problem is happening on meshes with many faces, you must be pushing the camera very close indeed, compared to the size of the faces, that is. I sometimes see something similar even with a well-subdivided plane if I place the camera at a very low angle to the plane surface, like a ground-level shot looking slightly up. The faces immediately in front of the camera don’t always render properly, with artifacts similar to what you show. Raising the camera slightly or increasing the angle between camera and ground plane usually fixes it.
The webspeak is ok for me, the difficulty is to find the dictionnary wich gives me the traduction 
Thank you for the answers