MS Analysis Services loop in the schema

I'm working in MS Analysis Services version v8.00.382.  I have two
dimension tables that I use in all my cubes.  Every time I enter to
edit a cube, these two dimension tables have a useless join between
them, and of course if I try to do anything I get the message, "There
is a loop in the schema.  Please remove the extra joins."

The two columns which end up being joined are related, but have
different names.

It did not always do this.  What must I have done to make Analysis
Services think that these two columns must be joined every single
time?  Is there a way to make this behavior go away, e.g. with an
option in Analysis Manager or dropping a foreign key relationship in
the original tables?

Thanks in advance.