Whaaat?

My Photoshop CS2 is screwing up on me, and I don't know why. Sometimes, when I open an image and crop etc. and change the size to 100x100, the icon base shows up as the correct size. But the rest of the time, the resized crop shows up maybe two or three times smaller than it should be, while the proportions still say 100x100. Can someone tell me how to fix this / what I'm going wrong?