If you see this error that means that you don't uploaded all theme files with replace. Try to reupload all theme files, and check that you replace files in existing folders, some FTP upload applications can wrong upload files. We reccomend you to use FileZilla application to upload files.
Check that all files from theme "app" folder uploaded to your FTP.
Also you can get this error if your Magento get some problems in previous updates (you updated it incorrectly). In this case your Magento installation is broken and you will need to use fresh installation to install theme.