Memory card won't show up on my mac?

I recently bought a nikon camera, but now when i tried putting the memory card into my mac it won't show up. The memory card is a Lexar 8gb and on my mac, it won't show up anywhere! I can't find it and since i'm on vacation I really need to upload many pictures. Please help out! The memory card isn't broken since it works on my sister's mac. Any thoughts?

I would check the disk utility with the memory card plugged in. If you can see it in there but can't access it, then I would renew the permissions, if you can't see it in the disk utility then you either have a problem with the card slot reader (if you have one bulit in) or you need to look at the setup of your camera which you have connected to the mac. If you do have a problem with the card slot reader then you could always plug the camera into the USB and see if access will work that way.