arping doesn't work: sends discovery packets to wrong MAC address

I know a tool arping, which I used successfully in the past. But today when I tried it, it failed to ping a host which is alive.

My IP address in local network is 192.168.1.20. Other computer's address is 192.168.1.63. If I do:

arping -I eth0 192.168.1.63

I see no responses. If I just ping 192.168.63, it works, and ARP resolution works too, of course. Tcpdump shows that arping sends it's ARP requests (who has 192.168.1.63) to MAC address ff:1a:ff:24:00:b8 instead of broadcast. When I do ping, ARP requests goes to normal broadcast ff:ff:ff:ff:ff:ff, and there is a reply.

What's wrong with my arping?

P.S. System is Ubuntu 10.10.