Fireworks Brush Tool Lag

[Tokiopop]

It used to be fine, but suddenly it started being really laggy. All the other tool work just fine, but when I use the brush tool it's very jerky and slow, and almost impossible to use.

I've tried searching Google, but everyone just seems to say turn Aero off, but I'm using OSX

Does anyone know why it's doing this? Is there a fix?

Edit: Now other things seem to be laggy. Mainly the eraser and blur tools. ARGH.