Re: A built-in function tried to access memory outside the Heap or Screen range
EDIT: You image only partially loaded -- now I can see the whole thing.
The VM Emulator assumes that the built-in functions should only be able to access RAM in the Heap or the Screen (and Keyboard). So the error is saying that you've set things up so that it will try to access RAM outside those regions, either down in low memory or above the Keyboard memory space. Another common cause is trying access memory at a negative location.
What SHOULD be on top of the stack before calling the readInt() function? What IS on the top of the stack?