My 2008 300C did basically the same thing on the way to church 2 sundays ago, I stopped at a red lite and I heard a chime, ACC not availible, it went out but when I attempted to move it acted like it was in neutral and started to roll back, I shifted to park and back to drive and it still didnt want to move, a few more cycles and I got it to go but it wouldnt shift out of 1st, side of the road, on to church, attempted to back into a space, again like its in neutral, into park and then to reverse it moved, after church no problems. I took it to the dealer the next day, oh you have to have an appointment to have it diagnosed, ok 10 tomorrow. tomorow arrives I show up at 10 we'll call you if theres a problem, wait you made me wait an entire day just to park it in the lot and you'll get to it when you can, and oh by the way we want 139.00 to find out whats wrong, Im pissed but ok call me. Next day no call, the day after no call, I call them, leave a message, they finally call and say come get it and dont forget the 139.00, I get down there and its we were'nt able to duplicate the problem you described, dont know what went wrong, gimme my money. Then she tells me we need to crack the tranny and do a flush and hydro fluid swap along with filter, because the fluid smells burnt, and if we find any shavings we will have to replace the tranny, 4000.00, lady give me my keys, I will never let you touch my car again. HOW do you see/smell tranny fluid in a car that doesnt have a dipstick, or maybe they think Im the dipstick. you gotta crack it open to determine these things, which they did not. NO its just another stealership trying to get me to bite. Oh they wanted 270.00 more to do the flush/filter/swap, I took it to AAMCO and they charged me 150.00. TODAY the same exact thing happened at the same red lite, ACC NOT AVAILIBLE, it goes off, I try to go and it rolls back, side of the road, no matter how many times I shift back to park, it will not shift out of 1st, brought it back home, back to AAMCO tuesday, after reading these post Im confident of the problem, but I want to hear what they tell me. Nice to have prior knowledge before going in to shop. I had this happen to me on a Chevelle back in the early 70's I had just bought the car used the day before, took it back, in the shop 30 minutes, never had another problem, they said the kick down module had gone bad, and one other thing can I replace it myself. Thanks