Gil,

You didn't include the opening ORG for your interrupt init'l. As shown it looks like Pranav is right. You might try:

ORG 0
jmp init

ORG 3H
jmp ext0_service

ORG 13H
jmp ext1_service

ORG 40H
init:
SETB EXO
SETB IT0
CLR PX0 ; LOW PRIORITY

SETB EX1
SETB IT1
SETB PX1 ; HIGH PRIORITY

SETB EA

main:
sjmp $

ex0_service:
-service here-
reti

ex1_service:
-service here-
reti

no need to reset IE0/IE1.

regards,
p