With the preview window open to see different kits, I clicked and held the left side of the window to drag and make the window larger. When doing that the window snapped to the left side of my desktop outside of the creation kit window and the width of the window became an inch instead of the normal size. I cannot modify the size of the window after this point without restarting the creation kit.

i'm having the exact same problem, except the window is permanently an inch or so wide, regardless of if I restart CK or not.