Have you tried deleting the cache file from the configuration folder? It seems like you might be experiencing a problem related to this, here is a link with the instructions for deleting this file.
If the issue persists then there might be a corruption of the configuration folder, if this is the case then you will need to rename or delete it to have it be recreated properly. Here is a link to the steps you can take for this:
Please post back to let us know how this works for you.