solution here: http://code.google.com/p/chromium/issues/detail?id=91666
To purge all breakpoints open inspector on inspector (undock first
inspector and hit ctrl-shift-I to open the second) and run
“WebInspector.settings.domBreakpoints.set([])” in second inspector’s
console.
2021 Edit: This answer is now a decade old, there are multiple alternatives in the comments to this answer. I haven’t tested them, the most up to date is from @reuben-thompson: window.localStorage.clear()