This is the common error message in magento and can be resolved easily. You will need access of your file manager or FTP.
- Login to cpanel.
- Click on File manager under files section.
- After that you have to navigate to /app/code/core/Mage/GoogleCheckout/etc/ path
- At this path you can see adminhtml.xml, config.xml, system.xml, wsdl.xml, and wsi.xml files, you have to remove all the files except config.xml file.
- Now check your website will be working.