I noticed something weird with Sarbian's patched version when using the ascent guidance: I'm currently building up a space station and lifting up quite a few similar to nearly identical payloads with the same lifter. (And for the sake of testing it also happened with identical payloads) Lift 1, no problem – love the force roll option for docking! Lift 2, again, no problem. Lift 3, the rocket won't lift off, no matter how often I reset, go back to Space Center/VAB and try to relaunch the rocket. It's spinning to the sides, doing loops and in the end crashes. This is also persistent after going back to the main menu and loading the save again. Only solution is to restart KSP. Then it's possible to launch another two rockets, the third will freak out again until the next restart of KSP.