I have tested it again. It seems that irexec is broken with kernel 3.8. When I copy my lircrc file on the live cd and that I restart lirc I get the bug. The one thing I haven't tested is the lircrc configs, maybe mine is weird.
How to reproduce:
(1) Start 13.04 live cd
(2) sudo apt-get install lirc
(3) sudo nano /etc/lirc/lircrc
(4) copy your config, here is mine:
Could someone try to reproduce it?
remote = devinput
button = KEY_POWER
prog = irexec
repeat = 0
config = python /home/script.py