Blank entry input page
Usually when you see this, PHP is running out of memory trying to load the page.  Bump your php.ini file's memory_limit setting to something higher and that should fix it.

Update:

Actually, this is in your phperrors.log file:

[23-Sep-2014 15:11:20 UTC] PHP Fatal error:  Maximum function nesting level of '100' reached, aborting!


See here for the fix.