SSL Broken?

In trying to add an SSL cert into Webmin, as I did exactly the same on several other systems successfully, I got the following error:

Failed to save new key : Missing or invalid PEM format key and certificate
 
Call Stack Trace
 
File    Line    Function
/usr/libexec/webmin/webmin/savekey.cgi  22  WebminCore::error
(eval 49)   6   (eval)
/usr/libexec/webmin/miniserv.pl 2398    (eval)
/usr/libexec/webmin/miniserv.pl 914 miniserv::handle_request

What am I missing? It worked on 6 other installs the exact same way just fine.