Proportional Edit Falloff won't work

Proportional edit falloff is extremely useful .But for some reason, it’s just stopped working.

It’s definitely turned on, I’m in edit mode, and trying to move a vertice, and only that vertice is moving. I can’t seem to use the mousewheel to adjust the radius.

I checked the little menu, and it’s definitely set to ON. What else could be wrong?

Edit: restarting blender fixed it. hmm

v2.45 is this a known bug?