For some reason, after you rename the tables in your LINQ to SQL diagram, you have to close the diagram and reload it in order for the new names to take effect.  The names change in the diagram in real time, however they are not seen programmatically untill you reload the diagram.  The same thing happened to me.  I'm afraid it may be similar to the cashing issue in another topic on this forum which we are currently waiting on a work around for.