Blank Card

Why does my G1 to say that my SD card is blank?
In my notifications box goes blank SD card. And I can take pictures and when I try of favor, it says insert the SD card although it's there. Lets show any of my pictures or recording videos, but I have them! I asked mobile workers in the mall and told to safely remove the SD card, but do not know how! Please help thanks a bunch!
Try do this: From the main menu press the screen, go to System Settings, and your SD card storage, and select Remove the SD card. This will will safely remove the SD card without deleting anything. If that fails, then you may want to take your phone to a T-Mobile store and let you see it.
