Thanks for your help! Managed to get it working... finally!
Tried this way: "make mrproper", make modules, install lirc but no luck.
It seems that for some reason it worked only after I removed /usr/src/linux-* and untar sources again, cp /boot/config-2.6.20*, make menuconfig, make modules, install lirc
I allways thought "make mrproper" cleans the sources, but... ?