I'm not sure I understand your question, exactly. However, I didn't notice something in the examples you provided. Which may, or may not, be related. Your URL is case sensitive, so the first one you posted is invalid with or without the
www.
VALID
http://www.cdlassociation.com/blogs/CPAP.htm
http://cdlassociation.com/blogs/CPAP.htm
INVALID
http://www.cdlassociation.com/blogs/cpap.htm
http://cdlassociation.com/blogs/cpap.htm