Interesting... so they return with something like STI/RETF 2 instead of IRET? I could hook the INTs and force such a condition to test the game with... which ones?
EDIT: I tried it with INT 13, and it does prevent the hang. A simple TSR that hooks INT 13 and does:
1pushf 2call oldint13 3sti 4retf 2
The INT 13 emulation code for the crack handles certain operations, but passes some through to BIOS. The ones passed through could be making up for the handled ones that disable interrupts. I guess a BIOS disassembly could "prove" the theory...