That thing is either written to your /etc/hostname or assigned by the dhcp client.
Either way, hostname of your computer should be resolvable; there might be some problem with the domain search patch in /etc/resolv.conf.
Other way to fix the problem is to put a proper line to /etc/hosts, something like
127.0.0.1 nicenameyoulike localhost x1-6-00-03-47-39-f7-ad
. Or you can deny dhcp client to change your hostname in the first place.