Question
Today I notices that the leaves on one side of my 7 year old sago pine are turning yellow. What is causing this and what can I do to save this beautiful pine?

Answer
I have not heard of a "sago pine" but I think you may be referring to a sago palm. Here is a link to a site that discribes problems with sago palm leaves.

http://www.junglemusic.net/cycadadvice/cycad-my-cycad-is-in-trouble2.htm

I hope this helps.