Photoshop :: My Brushes Won't Draw Anything

i've had this problem with my photoshop CS for a long time now, and have not been able to find anything in the photoshop help section, nor google that explains it or can tell me how to fix it. for some reason, when i try to use the brush tool NOTHING happens. alternatively if i switch to the pen tool, i can draw fine! then i switch back to brushes and nothing. it's not a layer thing, because i can open a brand new blank white window and try to draw on it and it won't work. i've made sure that i'm not drawing white on white (duh), and it's just odd that the pencil would work but brushes won't.