When you uninstall the add on does it seem to be successful in that? When you are in ExWeb can you see the add on listed in the add on menu?
It sounds like you have taken the correct steps to uninstall and reinstall so I'm not sure why you would not be able to create a new page with it. Is uninstalling your ExWeb an option for you? I'm not sure if this would help but if you are able this may be the next step to take.