I configured the system to use a new SSL cert for webmin, which apparently works, as I can get to the site via SSL with no browser warnings, but all I get on the left-hand column menu is System Information and Switch User. On the top/center screen, all I have is a System window which shows basic server information (e.g. Webmin v. 1.480). Clicking on Switch User just returns the same screen.
This happened immediately upon configuring the certificate. It is from GoDaddy (Starfield Tech) and is a chained cert. Right after I applied the changes I saw some kind of message about authentication and then I was out and unable to get back in.
I searched for this issue - my apologies if it's a quick fix that I missed.