Have you tried it on another PC? Does it copy quicker or is it also slow? So what I would suggest is establishing if it's the card, or the hardware transferring the data. If another PC does it much quicker then you can remove the card from the equation, if its the same then the issue points to the card its self.
I am sure you have sufficient memory in your PC, there is no a virus checking checking all the data going on and off the card etc.. ?
Phil.