Well after a little more fiddling about I have found that I can now use cat6.3 with out the problem if I install just the drivers and use AtiTrayTools and not the CCC.
So for me it looks like the problem is being caused by something the Crapalyst Control Centre is installing or setting
Impy
So for me it looks like the problem is being caused by something the Crapalyst Control Centre is installing or setting

Impy