What causes a flashplayer plugin bad image error, and how do I get rid of it?

I keep getting a nasty pop up box that reads "FlashPlayer Plugin bad image error etc etc" whenever I try to load a video or sometimes when I try to access my sites that require a special username and password. I have to click on it 3 times to close it, but then it pops back up shortly thereafter; it sometimes disables the video entirely. I tried to restore the computer to an earlier point, and at first it worked, but now it has come back. Very frustrating