|Being that it is happening on so many cards...I would guess that your card reader crashed out on you.|
Most card readers are installed using a USB connection. You might look at uninstalling the reader and then reinstalling it to see if the USB driver just got corrupted.
Start > r. clk. My Computer > Properties > Hardware tab > Device Manager button > look for the USB hardware and dbl. click on the card reader and then choose driver tab and choose to uninstall the driver.
shut down the system and re boot and allow windows to reinstall the hardware.
Change Is Good