Photoshop brush softness/hardness stopped working?

It’s the most bizarre thing! The softness/hardness of my brushes has stopped working entirely…I don’t get what’s going on. I even tried re-installing photoshop (CS3). You can still move the slider to adjust the “hardness”…but it has absolutely no effect on the brush, it remains at 100%!

Has this happened to anyone else?? I checked my CS2 and it’s still working fine. I’m completely stumped and frustrated. I also tried reloading my brushes…still none of them will soften.