Hi!
I have recalculated things and...actually it is not very difficult. I can now read 2 RFID-s simultaneously. I have PIC16F628 running at 11.0592MHz (comm's crystal). RFID's generate a port change interrupt and first thing the int routine does is saving readers port data.
This is one possible way to solve the problem. Probably there are others as well.
/Felch

PS. I use assembly language, Basic seems to bee too slow.