i downloaded "image and flash blocker" to get rid of automatically-playing video pop-ups, but now i can't play any videos! help!

to stop annoying automatically-playing videos on various sites (like cnn.com), i tried the "ask to activate" setting on shockwave or flash and it still happened, so i was directed to the firefox site that had the IMAGE AND FLASHBLOCKER to install and now nothing plays! i tried on youtube, for example, and i can hear sound, but there is no video. i can't find what i installed to uninstall it! have no idea what to do now .