Error with Photoshop 7 paint brush

Just recently my version of Photoshop 7 has been acting funny on my Windows XP Professional. My brushes will only paint white, no matter what color I choose from the color pallette. The time it happened was when I quickly set by brushes to default to find a certain brush. I have no clue what could have caused the brush tool to suddenly start this awkard behavior. Does anyone know of this occuring to others and if they know how to fix it? I have tried uninstalling and reinstalling, but it had no effect.
Thank you in advance.

Check your blend mode.

And if you're using a tablet, flip over the stylus so you're no longer using the eraser.