Here is a list of possible things to try and fix this error

  • Try flushing the Magento Cache or an external Cache systems like APC or Varnish
  • Disable Magento Compilation
    • System/Tools/Compilation
  • If using the Magento Novaworks Theme then "Disable" HTML Compression
    • System/Configuration
    • Novaworks/HTML Compression
    • Then Flush the Magento Cache