My problem i can keep really short.
When rendering, it only renders 1 second of the movie.
So i thought maybe the project was corrupt, and i opened a project i had rendered allready.
Even here it rendered only 1 second.
I haven't changed any of my settings.
What could be the problem?

Edit: After starting up the program again and trying again, it saves more then 1 second, in fact, it renders the normal length.
What could have been the problem, because i'd like to understand

have you enough space on the HD?
Have you set a max files size in the render section (if there is one)
are you rendering a region, which is at 1 second.

Yup, enough space.
Max file size and rendering a section..i don't know how to do that really