My passport is not recognized on mac

I bought my passport yesterday. It worked on my mac, today i copied some of my photos there and when i wanted to copy the other part of them my iphoto stopped responding. I closed it and then wanted to disconnect my wd but it didnt let me, i tried many times but with no result. I had nothing to do but just take the cable off, after that my mac doesnt see my wd, but when i connect it i can use smartware.

Please help me.

Are you connecting the device with a exstention or usb hub? It sounds as if the device is not receiving enough power.

If you unplugged the cable while the drive was in use, you may have corrupted the data, you may reformat the drive.