Stop The Crop Snapping
Problem: When you’re trying to crop an image using the Crop tool (C), your cropping border tries to snap to the edges of your document window. This might also be happening when drawing large Marquee selections as well. Solution: Press Command-Shift-; (PC: Control-Shift-;), which is the shortcut for turning off this snapping. The only downside is it turns off all snapping (like Snap To Guides, Snap To Grid, etc.). If you just want the Crop snapping (or Marquee snapping) off, go under the View menu, under Snap To, and choose Document Bounds, and your tools will no longer try to snap to your, well, document bounds.
Or you can just press CTRL while holding the mouse button down which deactivates snapping for the duration the key is pressed. Less clicks, more workarounds.
I turned of every snap I could find, in view and in preferences, and it still snaps. Holding down ctrl or ctrl+shift disables the marquee tool. Grrr! What else do I have to do?