You need to follow the instructions given by Patchou in this thread:
http://shoutbox.menthix.net/showthread.php?tid=21598
(and follow the instructions exactly! If it states "close every window of your browser", then you need to close every window of your browser!)
But that is only if you didn't tried to remove it yourself with anti-adware tools, because those will corrupt the uninstaller. So if you did that, you need first to install Plus! again WITH the sponsor to FIX the uninstaller and then follow Patchou's instructions...
/ 
