I now have trouble navigating my magento admin interface. We did not change anything that would warrant the sales, catalog, customers, promotions, rentals (from our sales igniter extension), reports and system tabs to stop working. We operate in a Parallels Plesk VPS. Also, we cannot edit any pages on the cms page, only preview. The website functions properly but the admin interface is nearly entirely broken.
If they are not, you may want to check if your file permissions are set correctly as it can be messed up after using Magento Connect Manager or Magento Backup.