Hold the 'Open door' button on your keyfob until all the windows go down, then keep holding it for a further 2 seconds.
Then roll them back up again.
Mine started doing this for a bit on my last car, and this seemed to cure it. If I was sitting on my keys the range must have been tremendous as I was about 1/4 of mile away, and thank god the car was in a high security car park!