Problem in reading memory cards of NIKON D80

What is the error message? If it is ERR then ERR message is not a good thing. Read page 132 of the D80 Manual. Also, try a factory reset found on page 129 of the manual. On the left side of the camera is the terminal cover, inside below the USB connector is the reset switch. If that does not work then it will need to go call Nikon digital 1-800-645-6689.

If you are using a 4GB or higher SD card, some computers cannot read it directly from their in-built SD reader. Buy an external card reader and plug it in. Your computer should now be able to read cards 4GB and larger

You can try to a SD card adapter for the USB slot and download without the camera. The adapter is pretty cheap and sometimes comes with the SD Card.

The PC reads the camera as an external drive, make sure your PC and OS is up to date.

the sd card slot is designed in such a way that when you push your card inside the slot till the deepest part and when yout leave it, it fits into the slot. if you want to take the card out you have to push the card again till the deep and leave to get it out.(just like a spring aided trap). i dont think that your slot is damaged.may be you are unsure how to insert the card in the slot. if you still find problems, please write back.

service camera at Nikon. mechanical SD card lock failure

See fix 4 http://camerarepair.blogspot.com/2009/07/simple-fix-for-memory-card-locked-error.html?m=1

I know that an SD card could lose it's little lock if it is damaged, the worse place is in the slot where it would block another card from seating fully. (don't force it) Even in a padded case if the sd cards are sliding around loose the can get damaged or even get dirt, lint or fuzz in the "lock".  If this has happened don't probe around in there, if you do there may be further damage done, that one a camera repair shop might be able to do or you may have to send it to Nikon for repair.  Don't have the camera on or even the battery in if you can't resist trying and don't stick anything metallic in the slot.
randy320sgi

Is it slightly thicker on the contact end, Or is something stuck on the flat corner? try getting a needle and picking out any plastic that could be stuck there. Is the card under warranty? 

Can it be pushed into the slot any farther?

My camera is now fixed. It was a tiny speck of dirt on the sensors between the mounting of the lense & the camera. The uy that fixed it said it is a problem with the camera because they are so sensitive.