Hi station_two, thanks for your quick response.
I can confirm that its not the card reader/cable, usb port, defective sd card or the computer itself. I have already eliminated all these potential culprits through trial and error using different several ports/cards/readers and even a different computer (although not into bridge).
I am able to copy the photos from the same card/card reader into Lightroom on the same computer (incidentally, when using Lightroom it uses the term 'Import photos'!)
I am using a number of Panasonic Lumix Micro 4/3s cameras (GH1/GF1/GX1). The sd cards have a combination of RAW and JPEG and the problem exists whether using 4GB or 16GB cards. I have plenty of space left on my hard drive and as stated, I'm running a fast desktop PC (Win 7 Ultimate 64 bit OS) so I'm certain this is not the issue.
Could this possibly be a problem with the cache?