Had a similar problem and found a solution.

Just open the /dolphin/inc/header.inc.php and find the $dir['root'] variable. See its contents!!
In my case the directory was set wrong.
It was "//peskovnik/Dolphin6/" instead of being "/domains/lahkonoc.net/public_html/peskovnik/Dolphin6/". So just enter your full absolute path and it should work just fine.

It worked for me.