problem with NECIRrcv

HI.

first of all I can catch my remote controller's signal with pulseIn() function.

but, what the problem is i cannot get any signal with NECIRrcv library.

i downloaded it and then copy& paste the example code (http://arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1210243556Link)

i dont have any problem to compliling it.
but i doesn't work at all.

the thing only i can see is "NEC IR code reception" msg.

My arduino works 20Mhz.
(without this, everything is same Arduino mini)
so i changed SYSCLOCK to 20000000 in NECIRrcv.h

what's wrong with my configuration?

is there anyone help me?!

thank you.