To me this seems like you don't need more than 2 tables. List and TaskList.

create table List

(

ListID int identity primary key,

UserID int not null,

ListName varchar(50) not null

)

create table TaskList

(

TaskListID int identity primary key,

ListID int not null,

TaskName varchar(50) not null,

SortOrder int not null

)

Then you just need to create the foreign key to your UserID and ListID.

From what you posted it looked like it was very possibly going to be over-normalized. For example making Task as a lookup table is probably a bit overkill. You might end up with a little duplication but that is probably not a big deal in this case.