A client of mine decided to go ahead and move from a self-signed certificate to a commercial one ("GoDaddy Standard SSL"). The first service I wanted to move to the commercial SSL cert was Webmin/Usermin... However, upon migrating to the new SSL cert and restarting Webmin, I got the following error:

[21/Oct/2012:13:12:47 -0400] Restarting
Failed to open SSL cert /etc/webmin/miniserv.cert at /usr/share/webmin/miniserv.pl line 4229.
Error: Webmin server did not write new PID file

And that's all it says.

Here's Webmin's config file (/etc/webmin/miniserv.conf):

port=10000
root=/usr/share/webmin
mimetypes=/usr/share/webmin/mime.types
addtype_cgi=internal/cgi
realm=Webmin Server
logfile=/var/webmin/miniserv.log
errorlog=/var/webmin/miniserv.error
pidfile=/var/webmin/miniserv.pid
logtime=168
ppath=
ssl=0
env_WEBMIN_CONFIG=/etc/webmin
env_WEBMIN_VAR=/var/webmin
atboot=1
logout=/etc/webmin/logout-flag
listen=10000
denyfile=\.pl$
log=1
blockhost_failures=5
blockhost_time=60
syslog=1
session=1
server=MiniServ/1.600
userfile=/etc/webmin/miniserv.users
keyfile=/etc/webmin/miniserv.pem
passwd_file=/etc/shadow
passwd_uindex=0
passwd_pindex=1
passwd_cindex=2
passwd_mindex=4
passwd_mode=0
preroot=virtual-server-theme
passdelay=1
sudo=1
sessiononly=/virtual-server/remote.cgi
preload=virtual-server=virtual-server/virtual-server-lib-funcs.pl virtual-server=virtual-server/feature-unix.pl virtual-server=virtual-server/feature-dir.pl virtual-server=virtual-server/feature-dns.pl virtual-server=virtual-server/feature-mail.pl virtual-server=virtual-server/feature-web.pl virtual-server=virtual-server/feature-webalizer.pl virtual-server=virtual-server/feature-ssl.pl virtual-server=virtual-server/feature-logrotate.pl virtual-server=virtual-server/feature-mysql.pl virtual-server=virtual-server/feature-postgres.pl virtual-server=virtual-server/feature-ftp.pl virtual-server=virtual-server/feature-spam.pl virtual-server=virtual-server/feature-virus.pl virtual-server=virtual-server/feature-webmin.pl virtual-server=virtual-server/feature-virt.pl virtual-server=virtual-server/feature-virt6.pl
anonymous=/virtualmin-mailman/unauthenticated=anonymous
premodules=WebminCore
logouttimes=
extracas=/etc/webmin/miniserv.chain
certfile=/etc/webmin/miniserv.cert
ssl_redirect=0

Here is a screen shot of the Webmin SSL config screen as well, for what it's worth:

http://postimage.org/image/r472go7tf/

Edited Mon Oct 22 10:45:24 CDT 2012:

When running the command openssl x509 -noout -text -in /etc/webmin/miniserv.cert as Falcon Momot suggested, I get the following error:

unable to load certificate
139760808240800:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:696:Expecting: TRUSTED CERTIFICATE