Data Wise Business Solutions

The Problem: 

1. if you have moved a site from one directory to another
2. you were prototyping a site with a different name.
3. Or you had a custom theam that changed while the old version was being used.

After the move or rename, you get a blank screen. 

The Solution:  

To verify there is a problem, look at the last few records of the sessions table.    If you see errors like “failed to open stream: No such file or directory in” then you do have to follow steps.

Step 1:   Edit settings.php file.
The file is located .../sites/<sitename>/

you may have to change the permissions of the file to allow for write

find this section:# $conf = array(
#   'site_name' => 'My Drupal site',
#   'theme_default' => 'minnelli',
#   'anonymous' => 'Visitor',

replace it with:
 $conf = array(
   'site_name' => 'My Drupal site',
   'theme_default' => 'minnelli');
#   'anonymous' => 'Visitor',

The site should now come up.  There will be errors and missing images

Step 2:  edit the files table records
for every record that has the old path, change the path.  

Step 3:   edit node_revisions table records
edit nodes that have hard coded image/file reference.  

Step 4:  Edit  settings.php file again
This time, put back the # char at the begin of each line.     This disables the forced theme.

DONE
Your site should be up and runing at this point.  

If it isn't, select a new theme.  using http://<sitename>/admin/build/themes