Aside from trying some fresh batteries, unless the camera holds some real sentimental value for you, I wouldn't spend a lot of time and resources at it. That is unless you want to learn something new. Non Super ME cameras can be had for a song, sometimes with some pretty nice lenses, on ebay. I have one that regardless of the meter reading and aperture setting, the shutter only fires at one speed (whatever the x sync is I suspect). I've had MEs and ME Supers that behaved exactly like you describe. Sold them for parts.