My Macbook Pro will not pick up my SD card

I have a Lexar 8GB SDHC card that my Macbook Pro 7,1 13" refuses to pick up. My camera reads it perfectly but when I insert my SD card into the card reader it refuses to work. I have been using it for months and it's worked perfectly up until now.

I've tried flicking the unlock/lock switch and it doesn't work on either. It works if I insert the card into the camera and connect using a USB cable, but as this is cumbersome and irritating, I would like to get my card reader working again. I have also tried restarting the computer with the card in the reader and this doesn't work either.

Please help.

Is it only this SD card that doesn't fails or every SD card? If every SD card, then you might have a broken SD card reader and might have to purchase a external USB reader.

I haven't tried another SD card. It might be worth noting that when it did work, it would only pick it up when it was unlocked while my camera only reads it if it's locked. (Or the other way round; it doesn't specify on the card itself)

First I would try a different sd card to see if it's the card or the reader. I have had card readers that just stop working.