My Moto Droid keeps saying SD Card removed in the notification bar when I pull it down it says insert new one

. I've takin it out and rebooted the phone fifty times, with and without my SD card in it is inserted correctly and the notification wont go away. Now, I cant acces any of my files, music, pics, or anything. When I go into: settings, sd card phone storage, all of the sd card options are grayed out, and a little SD icon with and Exlamation point sits in my notification bar. When I plug my phone into my computers USB port, it just acts like a regular charger, it doesn't say anything about being pluged into the USB port. I'm going nuts trying to figure this out somebody please help me.