SD card slot - Please insert a disk into Secure Digital Storage Device

I have a new Inspiron 1420 laptop.  The SD card slot worked when I first got the computer. Now it tells me to insert a disk into the slot. When I open My Computer and insert the card, it comes up with an SD card icon (icon looks like an SD card) but gives the message as above (message subject).  I've gone to the help sites in Dell, done google searches. I updated through Windows. Updated through Dell drivers, etc. I see that I'm not the only one with this problem. When I right-click and choose Explore, it shows the SD card is full.  I've tried other cards and get the same results.  I've checked the cards on other computers. Work fine. I also have a USB thumb drive that allows me to insert an SD card and read through USB. Works fine. Shows my files. So it's definitely the SD slot.  I've also gone into Manage through the My Computer icon, then choose Disk Management.  If I try to open that with the SD card inserted, it won't show any disks. As soon as I remove it, up comes the C drive and DVD drive.  When I re-insert the SD card, it shows up momentarily and shows the details (size) and then goes away.  I had read something about the voltage being an issue. There is no settings that I can find to tell the slot that it needs more voltage. I have the laptop plugged in and fully charged.  Thanks for any help.

Pat