Card Reader Stopped Working

I am running Windows 7 on a Studio XPS 435T/9000.  I began getting messages that a USB device was not working, but I didn't notice anything wrong.  Now I see that my card reader won't read SD cards.  USB ports all work as do flash drives.  I reliably use Microsoft Security Essentials and now ran Comprehensive malware scan & repair done with Emsisoft Anti-Malware; Registry "cleaned" with Win Thruster; hard drive "cleaned" with Win Sweeper. 

I don't see the card reader in my Device Manager display.

Please advise.