So, I was setting out on a late day trip to get a few things done. Maybe ~125 miles of driving planned. I also was planning to stop and try out the new CHAdeMO adapter since I would be within ~5 miles of a station. Anyway, car was acting a little oddly. Since the .167 update, during very light acceleration up to highway speeds I would feel a shudder from the rear somewhere between 30-40 MPH about 30% of the time. Was inconsistent enough that I chalked it up to something with torque sleep that needs tweaking and I was going to write Tesla about it tonight when I got back. This happened ~4 times today. Was heading down a 45 MPH road at about 57. Had the cruise set. No cars in front. Was taking a very slight curve in the road and the cruise disengaged by itself. No errors or anything, just as if I had tapped the brake or something. Hmm... so I resumed it and it went back to work. Less than half a mile later I disengaged cruise to regen to a stop to make a left at a light. A couple of seconds into that and I got this dreaded message: No other alerts showing either, just this one. Pretty sure I heard the contactors open (under light regen, was slightly downhill at the time) (Edit: Looking at my picture above more closely I see slight power draw from what I'd assume was the cabin heater... so maybe they didn't open?), car lost propulsion and regen immediately and behaved as if it were in neutral. I was going about 40 MPH at the time, and in this case I actually started to accelerate since I was initially using regen to slow for my upcoming left turn on the downhill. Last second I decided the left turn lane was not where I wanted to be without power, so I cut across to the right turn lane which was a bit larger of an area to stop safely. Parked in the picture above. Took a couple of pics. Called Tesla roadside/tech support (877-79-TESLA). Surprisingly was about 8 minutes to get someone on the line. While I was waiting I had gotten out of the car and was just pacing around aimlessly (I tend to do that when on the phone). My fiance was inside waiting. About 5 minutes into the hold time I heard the contactors close while standing outside the car. "Interesting," I said aloud to myself. I hopped back in, still on hold (~6 minutes). Car was fine. Started, put it in drive, and set course for home. Tesla rep got on the line right after this, and I explained everything to him. He was a little confused initially when I told him I was driving home. Long story short, he didn't have any immediate information. After asking multiple times if I felt safe driving home he put in a request for service to look at it and get back to me. Car made it home with no other errors or the shudder from the rear I had experienced prior. I decided to put off my errands until tomorrow, however, just to be safe. All of that said, I'm both concerned and relieved. Concerned because I have no real idea what the actual issue is/was. If I had to throw out a guess I'd say it has something to do with the latest update. Relieved because the car cleared the error on it's own and I was able to drive back home without needing a flatbed trip. Hopefully they figure it out, because I'm probably not driving it again until I get at least a cause nailed down by Tesla.