Wow - it actually worked
I finally got interrupts working in SoS! This means that I will be able to write a keyboard driver, and make a basic console.
It turned out that the problem was with clearing the memory that the IDT occupies - the way I was doing it (with memset) didn’t work at all, and was causing the code to crash when it received an interrupt.
The current SVN has very basic keyboard support, allowing you to type lower case letters. Currently the backspace, control, shift and keys like that don’t work… I’ll work on it after I’ve solved some other problems.