I'm using Ubuntu 12.10 64bits, and no render are happening - all are failing, although it was working before (1 month ago).
I de-installed, re-installed, no improvement.
I read on the forum that sometimes it works if you start kdenlive in root mode.
And effectively, it works, the rendering is starting again!
Anyone can advise what happenned?
What version of kdenlive? You shouldn't be needing to start as root and not advisable. Do you have ffmpeg from Ubuntu 12.10 repos or some other repo or self compiled?
Don't be concerned about the Decklink driver notice, just a bit of an annoyance about specific hardware for s specific purpose.
What is your source clip codec and what are you rendering to, also in your config how many threads for rendering are you using and what spec is your machine, RAM for example?
Do other transition types, Affine for example crash rendering? What about Pan and Zoom? I'm at a loss to suggest anymore? What are you compositing over your vidro files, maybe the problem lies there?
Try other effects, see if they crash rendering. Earlier you suggested it was something to do with Composite. To try to find out the possible reasons test your assumption, try other effects mentioned previously maybe.