there is definitely an issue with WP super cache
in 3.8 it is producing server error when trying to delete cache or most of the other actions. Debug is also not accessible.
Might be related to the .htaccess which is written by cache plugin.
Need to be fixed
Recommendation. DISABLE cache or better uninstall before update to 3.8
if not, you have a slowed down site
Best to remove the cache manually from server and let wp generate a new .htaccess file. A clean one