I have this problem as well.
Here the problem started when I clicked the option to delete out of date cached pages.
All pages went blank including the admin page. I changed the super-cache plugin directory on the server and the website was up and running again.
After uninstall the plugin via the plugin menu I reinstalled the plugin ans the prolem went back. It looks like the is been modified some (config) file..
Does someone have any clue?