I had the same issue and it finally turned out that my hostname was not configured inside of the /etc/hosts file. The error given by asadmin is somehow misleading. :-(
You could check if your hostname was correctly configured by:
ping `hostname`
If you get a "ping: unknown host" error you have to fix your hostname.
Login as root and fix your hostname using:
hostname "<YOUR_HOSTNAME>"
and to make it permanent by
echo "<YOUR_HOSTNAME>" > /etc/hostname
You also have to check that your /etc/hosts file contains a line like:
127.0.0.1 <YOUR_HOSTNAME>
after doing this you should not get the unknown host error when using ping.
I got the idea for the solutions from replies to this question.