I don't know if any of these will work but I don't think it would hurt go give one or more of them a try:
- Do a disk clean up; that will empty the temp folder, where temporary files are held. In additon, use the Run command, type in
%temp% and delete any files in there that you can.
- Run the error checking utility
This is a long shot, but maybe your memory card is becoming corrupted. After you remove the files from it, format the card.
Finally, get a new card reader or try downloading the images from the camera to the computer with the cable that came with it.
Related reading: format vs. erasing a memory card
http://www.digicamhelp.com/accessories/memory-cards/erasing.php