There is a simple fix for when the Linq to Sql designer goes crazy with the number of points on an association line. Simply close the designer, click "Show All Files" in your solution. You should now be able to expand the underlying files used to store info for the designer. Open the dataContextName.dbml.layout file with the XML Editor. Associations are stored in an associationConnector element. Find the correct association and change the following attributes to appear as follows:
manuallyRouted="false" fixedFrom="NotFixed" fixedTo="NotFixed"If manuallyRouted doesn't appear, don't worry about it. Save everything and close the file. Reopen the designer and your line still looks weird but as soon as you move one of the objects around, it should fix itself.