I have purchased AdBlock more than once. When I restart my computer AdBlock doesn't work at all. I have to delete it and reinstall. This is very annoying. I've checked for system or extension conflicts and can find one. Something is happening to AdBlock when the PC is restarted but I can't figure out what it could be. Are you familiar with this issue? I should state that the PC is an old, bare-bones, Compaq Presario, running Vista, that I really only use for mail or news. I use my Mac for everything else. I've never really installed anything else on the PC except Chrome. It's a enigma, wrapped inside a mystery, that's causing me a fair amount of frustration.