There are two possibilities for this error:
The card is actually faulty and needs replacing.
The driver for the card reader is not installed or it's corrupted in which case you need to reinstall it.
Go to Device Manager (Start > Run > devmgmt.msc) and make sure that every device is properly configured. There shouldn't be any category expanded. In case there is one driver not installed, right click it and choose Update Driver. Alternatively, switch the card reader to another USB port if you connect it through USB.