Driving home last night the radio stopped working. I switched it off then on again and it briefly said LOCKED then resumed the radio station, then went off again. Indicater also froze in the ON position. Got home switched off car and fan was blowing very noisily and electric aerial would not retract even with keys removed. Tried to start engine again and it turned over but that's all it would do. Removed the 15A fuse for the radio and hey presto - the car started again. I'm now driving it around normally but with no radio as each time I insert the fuse the aerial goes up and the car won't start. What could be the cause?