I'm 100% certain it's because of the array revamp, because that was the whole major change when going from 1269 to 1280. My shop uses several arrays, which is also why I believe that is the cause.
When you go into the shop you get a separate "Microsoft Visual C++ Runtime Library" window which says:
"Runtime Error!
Program: ...ments and Settings\Tuggernuts\Desktop\1280\zelda-w.exe
This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information."
Here's a test quest to show the problem. From the start screen go left, down, and into the door that has a sword over it. Talk to the shop keeper and it'll crash. Try it in 1269 and the shop will work perfectly. This is a major bug, I can't let go of this shop since it's the backbone of the type of game I'm making (also since I've worked on the script for damn near a year on and off now.)