If your car's engine is running too hot, the fuel systems ECU will turn off voltage to the comprsssor as that's done to protect the engine from severe overheating, damage as heat from the condensor adds ALOT more heat to the incoming air that passes through the radiator. I've seen this happen before with 850s and if your t-stat's staying closed too long (temp guage reads higher than usual) or it's extremely hot outside while the car's not moving (little air passing through condensor and radiator), the AC can shut off.
It's been very hot here too lately (mid to high 90s and humid) and if I'm not moving, like stuck in traffic with the AC on, the engine will overheat (740T) so I have to watch the temp guage then and shut AC off if the guage reads too high until I'm moving again and my condensor fan's working too (new radiator, etc.). The AC looses efficiency when it's that hot and the car's not moving as the condensor's not able to give off enough heat.