You may be experiencing a problem with the cache file, here is a link to a document that details how to delete this file, please give this a try to see if it clears your issue:
common_installation_issues.pdf
If you continue to have this issue you may have some corruption of your configuration folder. Here are steps you can take to resolve this:
showpost.php?p=12293&postcount=2
If you continue to have this problem please let us know.