Look at your ray/modules/global/inc/header.inc.php file and make sure the settings are correct. I had this problem last night and after about 5 hours of messing with it I finally got it to work.
The problem with me was the "install" of Ray did not setup the directories correct and there appeared to be a line missing from this file.
This is the line that was missing....
include("/absolutepath/inc/header.inc.php";
absolutpath is the directory path to your dolphin install (eg. /usr/var/public_html/dolphin). The inc/header.inc.php is the dolphin's header.inc.php and not Rays. This line is the first line after the comments at the top of the file, around line 10.
Next Ray inserted the directory names into the following variables. I changed them back to what they originally were when I installed the full dolphin package (dolphin + orca + ray). Make sure yours looks like this:
/**
* General Settings
* URL and absolute path for the Ray location directory.
*/
$sRootPath = $dir['root'];
$sRootURL = $site['url'];
$sRayHomeDir = "ray/";
$sHomeUrl = $sRootURL . $sRayHomeDir;
$sHomePath = $sRootPath . $sRayHomeDir;
This got me past the blank screen. I had further problems with Ray after this but that is a different subject for another time.
If you get past the blank screen but then get a popup with a white background and two words "Not Installed" let me know and I go into how I fixed that on my system.