Thankfully James Shaw wrote a post about this a bit back. His was the only result returned when searching Google for the error message.
The answer: It’s System.Web.Profile.SqlProfileProvider not System.Web.Security.SqlProfileProvider.
Dan HounshellWeb geek, nerd, amateur maker. Likes: apis, node, motorcycles, sports, chickens, watches, food, Nashville, Savannah, Cincinnati and family.Dan Hounshell on Twitter