I understand the faulty memory problem. I've got it bad. Started when I turned 40.

This is a great page for info:
http://michigantelephone.workbench.net/

My guess is that your house has 4-wire daisy chained to the outlets. That would give you two lines. It's possible that one of the chains was broken when the dry loop was installed. They should have pulled a new cat3 or cat5 line for it as 4 wire isn't good for DSL.

The phone wiring in my old house was so old and cheap that I ended up pulling new cat5 to every room. Glad I did.