I'm pretty sure he means to get a new SD card. It might be corrupted.
Just so I understand everything, nothing appears on the SD card? And you formatted and it says to insert a disk when you try to hook it up via usb? It shouldn't be asking for anything like that. When you connect via usb in recovery it should display your phone's sd card in a folder just like you would expect and you should be able to copy files back and forth as you see fit.
If you've done all the formatting and still can't get your computer to see your SD card in recovery, then you may just have a bad micro SD card. Do you have another one that you could try? Even something with a few hundred megs would be enough size for you to get a rom on there and we could get you up and running. I have an old SD card from a previous phone that I could use if I absolutely had to.