This is a bug i found... I will walk you through it step by step to recreate the bug. Just make sure you DO NOT do this on a production server ;) It will put your site offline :O
Ok, select a virtual server, and go to Server Config -> Website Options
Now, under "Website documents sub-directory" try leaving it the same, but change the end of the directory.
ERROR: Website documents sub-directory must not begin or end with a /
Why is this a bug? Because its a full path to the folder, and full path's start with a / (at least in linux they do)
In fact, you dont even have to change the setting at all, I went in there to change from fcgi to cgi (I have WHMCS installed on the server). All I did was change the radio bubble and got the error...
So I took the first "/" out and hit save.
My website is no longer accessible. GREAT!
Its a damn good thing I know how to configure apache2 + virtual servers, all I did was find the config file (/etc/apache2/sites-enabled/) and manually change the document root's back. Restart apache, and voila! Your site is back :)
Now it still shows in virtualmin what I edited the "Website documents sub-directory" to, but I could care less...
Can i get vmin pro for free?? please?? lol ok maybe not :( wayyy too expensive IMO (i know you worked hard, but... pricey...)
Thanks anyways for the GPL version :D