Have you already tried clearing the cache file or renaming the configuration folder? Normally you should clear the cache file first, if this does not resolve the problem there might be a corruption issue with your configuration folder. Here are two links that detail the steps you will need to take for both of these.
Clear the cache file
common_installation_issues.pdf
Corrupt Config
showpost.php?p=12293&postcount=2
If after trying these you still have the error let us know so we can check it out some more.