Against all odds, I "fixed" my broken 50/1.8 tonight. Its wreckage was lying on the kitchen counter, and I picked it up to take a last look when started thinking, "Hey, this isn't as bad as it looks." I lined up the two pieces, and pop! It snapped back together. Hmmm, maybe I jumped the gun yesterday.
I flipped the manual focus switch, turned what passes for the plastic 50's focusing ring, and what do you know — it's working again. So I pulled it back apart, cleaned the front and rear elements on both sides, and popped it back on my camera for some test shots.
I thought it would go one of two ways. One, nothing happens, and since it doesn't have an aperture dial it would be stuck wide open. Or two, it works, but focus is slightly off.
You have probably guessed what happened — the lens works just like it always did. Pretty much. It's a little noisier when focusing now (apparently, that is possible). Plus, when it gets to either end of the focusing range, there's more of a clunk. I suspect it will be replaced for general use by the 28/1.8 once it arrives, but I can still use the 50 as a portrait lens on my 40D. And I'm happy to have my little friend back.
You know when you have one of those "yard sale" wrecks while skiing, and the little mechanism on the bindings causes your skis to fly off before your leg breaks? Maybe Canon has designed the plastic 50/1.8 to survive minor falls using the same principle. Yes, that must be exactly what they did.