I always used the number keys to set opacity in brush tool. Suddenly it now affects flow, not opacity. At the same time this functionality changed I started having to click on a mask for the [ ] keys to change brush size. I used to be able to change size without selecting the mask. Did I inadvertently change some setting? I am using CS5 12.0 x 64 on Mac in 10.6.8. Thanks !!!
You've probably enabled airbrush-style mode. There's a switch in Options bar.
That's it. You nailed it. Thanks !!!