Safari 4 on Mac OS X, although, I've ruled out my workstation.
EDIT: Hm, it's only that question. I can edit other questions fine.
I edited this question on SO to remove "I've never really understood" from the question, but when I click "Save my Edits" it goes gray and does not allow me to submit.
Switched over to Firefox (I keep Firefox in porn mode to avoid "did you clear your cache?" questions, and use it specifically for testing and dev), same there.