I just tried to install phpmyadmin for a client (a couple of times, as root and as server owner) and I get this in the httpd error log:
Not Found The requested URL /phpmyadmin/navigation.php was not found on this server.
Permissions on the folder created are 755.
Permissions of .php files in the 'phpmyadmin' folder are 750.
It does not prompt for credentials.
Virtualmin version 3.86 Pro
Any clues? I have used a few other scripts in the past without any issues.