I just found this on t'internet.
"Notice there is a little black plastic sleeve around the rewind release button. Inside the camera there is a groove around that sleeve, and when the button is pushed in, a spring-loaded cam arm clicks into that groove and holds the button in. When the winding lever motion begins, the cam arm is pushed out of the groove and releases the button.
If you have a small cross-head screwdriver, take off the bottom cover (three tiny screws, one toward each end and one in the middle). Don't lose the screws! You'll then be able to see the button, the black plastic sleeve around it, and the cam arm that fits into the groove.
With a small tool, gently press outward on the end of the cam arm nearest the winder shaft, and the other end of the cam arm should release the sleeve and the button. Then work the winding lever and shutter and try the rewind button again a few times to make sure your repair worked. On normal ME Supers, the beginning of the winding action (after the lever is popped out to winding position) should release the button.
If the metal shaft of the button is depressed but the plastic sleeve is not, try jiggling the toothed spindle inside the film compartment as geowelch suggests and work the winding lever and shutter again. With your fingertips, gently turn the sleeve on the shaft.
If the cocking action doesn't move the cam arm, or if the cam arm isn't moving enough to release the groove in the button sleeve, then the cam arm isn't making proper contact with the winding lever ratchet wheel and may be bent or worn. If the cam arm doesn't click into the groove, then the spring is probably broken or unhooked. These kinds of problems probably will require repair by a professional."
I'll give it a try in the morning!