Apparently MythBuntu (and MythTV under Ubuntu) will only support MythArchive if it is on the same machine as the backend. Basically, if you have a backend only machine you are unable to burn your recordings to a DVD from your front end machine. There is currently a bug open (118700) but, sadly, it doesnt seem like anyone has an interest in fixing it soonish. The good news is there is a very easy solution to the problem.
First, mount your recordings directory from your backend server on to your front end machine. This requires installing nfs.
apt-get install nfs-user-server
Add this line: /var/lib/mythtv/recordings 192.168.1.5(ro)
(Make sure you replace the IP address with your front end's IP)
Now you need to mount that on your front end machine.
apt-get install nfs-client
Add this line: 192.168.1.3:/var/lib/mythtv/recordings /mnt/recordings nfs
(Replace that IP address with your backend's IP; Make sure /mnt/recordings exists)
Now you need to add an entry to the mythconverg database. You can do this from either machine.
mysql -h 192.168.1.3 -u mythtv -p mythconverg
(Replace the IP with your database server - usually same as your backend)
Now you need to run this command at the mysql prompt:
insert into settings (value, data, hostname) VALUES ('RecordFilePrefix', '/mnt/recordings', 'myth-frontend');
(You'll need to change myth-frontend to whatever the hostname is of your front end)
That should take care of it
DISCLAIMER: I am not a database guy.... I don't even fully understand what that command does. I am simply taking information from the bug report and putting it in to a step by step list. I can confirm that this worked for me in my situation and it most likely will work for you. Reference Link