Photoshop freezing up?

Today I opened Photoshop CS4, and it froze when I selected my brush. I thought nothing of it, but every time I wanted to change my brush, it froze for a couple of seconds and then allowed me to change the brush. I thought it was using up too much system memory, but Task Manager said I was only using 100mb, so nothing out of the ordinary. I tried restarting, but it still happened. I haven’t installed anything recently that would impact this, so I’m trying to figure it out.