I've bought a few games recently, and every now and then, they get errors. I bought Monkey Island 2 and Indiana Jones & The Fate of Atlantis (had them for PC, not Amiga), both still boxed, but somehow one of the disks for Monkey Island 2 had managed to get an error on it. The problem is, with magnetic media (disks, tapes, etc) even if they're safely locked away in a cool, dark place, they're going to get errors because of the natural magnetic field caused by this planet. Unfortunate, but that's the way it is I guess.
Now, for trying to get your Simon the Sorcerer disk working, make sure you try it in a different drive for a start, one of the drives in my A2000 picked up errors on disks every two seconds, the other one didn't pick up any :lol:
Also, when it comes up with the 'error on block 1728' or whatever, click retry a few times, you never know if it will keep reading.
Lastly, if you read the CAPS FAQ, it talks about how to retrieve data off old floppies that have errors. They reckon that the 'Spin and Blow' method works well. By that, you have to keep the disk door open, and spin it around by the center metal piece, blowing into the disk to try and get rid of any dirt or foreign objects, etc. Make sure you don't spit in there though :lol: :-o
I've had that get a couple of floppies to work before, so give it a go. Otherwise, the other option is to try and download just the disk that's not working. Obviously it's not the best solution, but under your circumstances, it should be alright. Anyway, good luck with it :-)