Trying to find some photos, they're not on my old PC so I'm going through my old USB sticks. Plugged one particular one in, and it didn't show up in the finder. Plugged it into the other USB slot and it came up for a few minutes then when I went to look at what was in it it said that it had ejected. Now I can't get it to recognise at all. I've tried restarting my macbook, didn't work. Any ideas?