This one got me yesterday. Changed the admin password for a server while logged in on https://somedomain:port and now browsing gives you :
Forbidden You don't have permission to access / on this server.
Additionally, a 403 Forbidden error was encountered while trying to use an ErrorDocument to handle the request.
I thought it was the application so set the password back to the original and still get the same results. I thought I saw this come up as a question before but can't find it as applied.
I'm on CentOS 4.4 webmin 1.350-1 VMPro 3.40 usermin 1.280