[ubuntu] Can't change mirror address in interactive xm console screen

Hello all,

I am having some trouble installing an Ubuntu VM with Xen. I start by using the xen-create-image command with the appropriate
parameters.

I then run xm create <configfile>. After that, it shows up in the output from xm list.

When i then try and do an xm console <domain>, it gives me an Ubuntu installation screen (using the ncurses
text graphics tool, I imagine). Unfortunately, when I go to change the URL of the mirror, I can't edit the highlighted field.
For example, if I select Ireland as the county, it automatically places ie.archive.ubuntu.com in the field. the process
then fails because it can't connect to the mirror. i expect this as the field value is incorrect.
I want it to point to ftp.heanet.ie/mirrors/ubuntu/ but I can't edit the field at all.
Anybody know what's going on and how I can fix this?

Thanks

-- redmage123