Hi,
I have exactly the same error message when trying to activate the latest version of RokCommon.
Fatal error: Uncaught exception 'InvalidArgumentException' with message '[WARNING 1549] failed to load external entity "/Users/nick/Sites/appengine wordpress/Perfect Floors appengine-php-wordpress-starter-project_build_linux_mac/Perfect Floors/wordpress/wp-content/plugins/wp_rokcommon/config/wordpress.xml" (in n/a - line 0, column 0)' in /Users/nick/Sites/appengine wordpress/Perfect Floors appengine-php-wordpress-starter-project_build_linux_mac/Perfect Floors/wordpress/wp-content/plugins/wp_rokcommon/RokCommon/Service/Container/Loader/File/Xml.php:220 Stack trace: #0 /Users/nick/Sites/appengine wordpress/Perfect Floors appengine-php-wordpress-starter-project_build_linux_mac/Perfect Floors/wordpress/wp-content/plugins/wp_rokcommon/RokCommon/Service/Container/Loader/File/Xml.php(52): RokCommon_Service_Container_Loader_File_Xml->getFilesAsXml(Array) #1 /Users/nick/Sites/appengine wordpress/Perfect Floors appengine-php-wordpress-starter-project_build_linux_mac/Perfect Floors/wordpress/wp-content/plugins/wp_rokcommon/RokCommon in /Users/nick/Sites/appengine wordpress/Perfect Floors appengine-php-wordpress-starter-project_build_linux_mac/Perfect Floors/wordpress/wp-content/plugins/wp_rokcommon/RokCommon/Service/Container/Loader/File/Xml.php on line 220
You will note that this is being installed on a (local) Google App Engine Project.
The wordpress installation works perfectly and third party plugins install and activate fine - just RokCommon that's failing.