I had the same problem and found out how to fix it. You will need to access you php.ini file. This may be in the root of you server or only accessible through your hosting control panel. My hosting allows me to choose between PHP4 and PHP5.

I use PHP5

Find in you php.ini file
zend.ze1_compatibility_mode =

I then changed this to
zend.ze1_compatibility_mode = Off

Went back to check the site and presto! No error