Re: X won't start
*sigh*. After struggles, I managed to get 256.35 installed into the machine, and now X starts again. Interesting, since between the boots today I hadn't updated my kernel nor my drivers, yet X spontaneously broke down. Has happened before, though then reinstalling the distro provided drivers has been enough (not so this time).
I'll see when I get the flickering problem again and post debug logs. Hints on the freezing problem would still be needed, as there's nothing in any logs visible after reboot.