I'm having the mostly the same problem you have been discribing right now. Car drives fine at lower speeds and then when I take a corner at highers speeds(40-60mph) the whole back end whobbles. It actually only does it when I turn right, and never when I turned left. This is what led me to believe it was the back left wheel that was the problem, and sure enough that was the case.
I jacked the wheel up and spun the tire around. You could tell just by doing that that the wheel was completely bent.
I say check your wheels before you start tweeking with the suspension.
