2000 Mercury Cougar will not Move in any gear

Car runs great, sounds great, just charged the A/C, drove it to work several times, smells hot and burning and some light smoke coming from under hood. Then one day after a drive of maybe 6 miles I parked it, left it running to unload some stuff, left A/C on and cleaned interior winshield, got in it to back out and it would not move. Not in any gear. The break pedal seemed to not have any give in it when pushing on it at that moment. I turned it off and let it sit for an hour and then cranked it and it backed out just fine. My boyfriend took it another day to test it out and drove it for about 10 miles and while driving it just slowed down and would not go and he too said it felt like brakes were locking down but it wasn't a slam just a slowing down.