ci error when url parameter zero

[eluser]nhantam[/eluser]
My Application:

http://www.myweb.net/login/index/1
(catch status) run OK
but
http://www.myweb.net/login/index/0
error: "503 - Service Not Available"

Could you help me, How do I fix bug URL parameter zero ?
Thanks you very much

My server:
- lighttpd 1.4
- PHP 5.3