Probably the last thing that you wanted, but here goes:
Upon opening the live theme editor for the default 'TwentyEleven' (Although the problem is the same for any theme) PHP throws the error
'Fatal error: Cannot redeclare class Document_Revisions_Admin in /Applications/XAMPP/xamppfiles/htdocs/wp-content/plugins/wp-document-revisions/includes/admin.php on line 9'which means that the WordPress process has terminated and hence there is a blank screen in view (completely blank for servers with error reporting off). As you can see from the error, the class is upsetting it. At the moment there are no documents actually in the WP Document Revisions post type/section (whatever you want to call it) on this install.
Basic info: WordPress 3.4 UNIX server Apache PHP 5.3.1
Multisite install (subdomain type). This sometimes makes a difference...
Thanks in advance for listening.