NextDesign, I am so very much grateful to you and i can certainly say that this is the nicest thing anyone has done for me when i asked for some help online, regarding anything. Thank you so much.
That's so nice that i'm almost sorry that we managed to solve our problem before i read this post
Anyway, the problem wasn't the far clip plane, full RAM, or anything like that. It seems that somehow (i have no clue how) we had a "DefaultRenderLayer" created in our scene and that layer was checked as unrenderable. Anything that we created or changed after that layer was created seems to be put in that layer, therefor not renderable. (but interesting, still it was renderable as single frame) We haven't created that layer ourselves and have no clue how it was created, and WHY it had uncecked the "Renderable" box..
As for your script, thank you again for making the effort to help us, i will still test it out when we are done rendering. Hope this this thread and your script will help out some other desperate souls.