Finch......not your imagination. Have had our 2008 Edge for about 2 years now and have loved the way it handled in the snow and ice. This past weekend on Sat. night, then again on Sun. am ...TURNING A CORNER both times, I experienced the same problem and feeling. In fact, I described the problem almsot as you did. It felt as if the back tires were getting the call to push and they did! I pulled into a parking lot, shut the car off, started it, then noticed the anti-skid icon stayed lit, which, according to the owners manual....means system needs checked. Am taking it in today.
Oddly enough....had a dead battery and new one put in this past week. Could that be the cause? I have driven Colorado roads since driving age....and these two "spins" were not tire or sensor or driver issues. Nor have they been the norm for this car. Certainly feels as if something is causing the computer to send the wrong information to the wheels!