Shockwave Flash problem

Recently, my browser (Mozilla Firefox) has been giving me warnings that “shockwave has performed an illegal operation” and recommends shutting down and reopening the browser. My PC has been freezing, too, so I can only imagine the two things are connected (not, I don’t know if this happens with IE as well, I hardly ever use it now.) I uninstalled Shockwave Flash hoping it would solve the problem, but I’m still getting the warning. What’s up?