Crashes whole WP installation

Firefox tells me ‘The page isn’t redirecting properly’ and IE says ‘Internet Explorer cannot display the webpage’. I can’t access my site at all. I have tried to delete the plug-in folder via FTP and still the problem persists. I have to try and figure out where this has hooked into WP and unhook it else it means a complete re-install of my site. Not good for a simple ‘meant to be useful’ plugin!