I am having the same issue. I have the mage store and wp blog on the same server, with the magento store being served up on http://www.domain.com and the wp blog at subdomain.domain.com.
I am using a Linux server with plesk, and php is running as a php user. When enter the absolute or relative path to Mage.php in your extension, it keeps stating a invalid URL error.
I have even tried changing the location of the subdomain folder to be within the root folder of the mage store while targeting the WP blog to load on the subdomain, and still I continue to get the same error.
I thought maybe it was a file permission error, and made everything 755 and still no luck.
Any suggestions?
