The Six Stages of Debugging

Of course, if you Google for it you will see many people quoting this, but here is the original as formulated in RD5 while slaving away on Dante:

The Six Stages of Debugging

1. That can't happen.
2. That doesn't happen on my machine.
3. That shouldn't happen.
4. Why is that happening?
5. Oh, I see.
6. How did that ever work?