Hi, crop tool question

Hi, I'm new at icon making, and this community has been a lifesaver, but this time I couldn't find anything useful in the memories.
Everytime I cut an image (with the cut tool or the marquee+cut)it gets a 1 px black border. I tried everything I could think of to avoid it, or at least erase it, but nothing worked.
I saw a similar question posted recently, but I tried looking at the feathering setting, and it was already on 0...help!
Thank you ^_^