Corruption on Download Via a USB Port

I wonder if anybody can help with a problem I am experiencing on my PC with
downloading camera images from a compact flash card via a USB port.

What is happening is that when I download the images and then look in my
photo editing software I usually find that 3 - 6 images out of 100 - 150
are corrupt. If I redownload the corrupt images they then appear correctly
ie no corruption.

I have tried downloading in 3 ways connecting the camera via a USB port,
using a card reader on a USB port and connecting a FlashTrax (Portable
Storage Device) via a USB port and I get the same problem with all 3
connections. All 3 devices have their own USB cables and I have tried two
different USB ports in two different cards on the PC. I have no problems
with downloading on my laptop[ or on a friend's PC.

I know it is not a camera fault as I get the same problem with images I have
downloaded from a friend's camera (exactly the same model)

All this leads me to the conclusion that it must be something to do with the
USB port.

Any suggestions gratefully received

Tony Falla