4GB G-Skill RAM problem

[ben16]

On Vista my RAM has always been rated at 5.9, I just retested it and now it's saying 5.6?

Here's the cpu-z RAM page in case you can spot anything that's wrong:

 

[ben16]

Should the freqrency not be higher than that? I thought it was meant to be 800mhz:

http://www.overclockers.co.uk/showproduct.php?prodid=MY-019-GS

 

[ben16]

Any reason why Vista might suddenly downgrade its rating then?