Did this problem occur after an update of your site? I have seen this when a few files have become corrupt during the update process.
Here is what I would do if it were me in this situation.
Using Akeeba take a backup of your site.
Install a copy of that backup on your desktop using a tool such as WAMP, MAMP or XXAMP
Once you have it running locally you can play safely and test.
I would then overwrite all the Joomla files from the Joomla stable update package available from here – http://joomlacode.org/gf/project/joomla/frs/?action=index
Hopefully that will fix it. If it does you can do the same on your live site.
I also see some errors coming from Phoca Gallery so please re-install that.