Hi,
SORRY IT HAD NOTHING TO DO HERE (I HAD NOT SEEN ISSUES) AND THE PROBLEM WAS NOT YOURS. APOLOGIES.
I don’t know if it’s linked with the issue you had a few hours ago with your servers but while I could do the installation before, I am getting this error now.
The fact I have been installing it several times is just because I tried so far to install it but did not succeed.
On a fresh Ubuntu 14.04 install, first I got an error stating that virtualmin-server-manager and other virtualmin packages didn’t exist, then I added your repositories sources manually and it failed with the above error.
Thanks for your help