Problems: Read speed of Transcend 600x CF 16gb card

Hi,

My new Transcend 600x CF 16gb card reads very slow - when copying files to my PC I am getting speeds of 6MB / sec compared to 40-50 MB / s with the Transcend 400x cards.

I am reading this card in a USB 3.0 Transcend card reader and with a Transcend USB 3.0 PCI card installed.

I checked serial number and it appears the card is genuine. So I feel this is a compatibility issue - anybody faced with this problem before?
--
Blaise
Wedding Photographer Nice, France
http://en.photographe-mariages.net