Cannot remove lines...

Please help, I was drawing in DS. I had just added three simple lines when suddenly I was unable to select anything but these. I clicked in panick around the lines and then the problem switched, I could select any line except the three I had drawn. They are in layer 0 like the rest (they are hidden when I hide the layer). The weirdest thing is that when I zoom in or out, they always remain the same size and in the same location on the screen. Any ideas? Thanks!