what are the settings in the BIOS. you need to reboot and enter the BIOS and make sure that the RAM speed is set to 1333 or 667 (Double Data Rate) reboot and see if the RAM performs better.
make a note of the settings the RAM is set to now.
my ram speed is 1333 mhz but when i OC my cpu it jumps up to 1400mhz and makes the system very unstable, so i underclock it to 1200mhz which it then overclocked to 1300 mhz.... i cant get exact 1333mhz though.