USR function (*solved*)

[boriel]

Probably because the default UDG address PEEK UINTEGER 23675) points to top of memory (ZX Default), which is now being used by the compiled code and the heap.

Try this at top of your code:

Code:

#include <alloc.bas>
POKE Uinteger 23675, allocate(20 * 8) ' 20 Chars * 8 bytes each

This points UDG Address to the a free reserved mem area, so It won't get corrupted.
Note: --spectrum parameter does this by default.