The most common problem is the 1.2 Patch. You've said you have that so here are some things to try...
1) Start a fresh game. Go to Midas' shop right from there. Save before entering.
2) Ring the Doorbell. Does it crash?
3) Enter. Does it crash?
If not on either, in your original game. Save before entering Midas' shop and wait 3 game days. Hit the doorbell and then try to enter.
If I ring the doorbell, it crashes, but I can enter and talk/interact with everyone normally, I mean Midas is willing to sell me 1 spell, that one monk gives me a quest to kill the snipe, I can read the books, its just the actual spellmaking devices, laboratory and doorbell which crashes it...Im about to try the waiting 3 days ingame one...
EDIT: Yep, It still crashes after waiting 3 days in front of the shop and pressing the doorbell. Darnit...btw, I've got a question which may sound pretty stupid but I want to make sure, on the Main Menu of the game, with the options:Continue, Load, New Game, Options, Credits and where the title music plays, at the bottom left corner of the screen it says 1.2.416. That does mean it is patch 1.2.416 right?