That explains your problem but I need more details to tell you exactly what you need to do. Do you have the basket looking clump in the middle, or did you have the tall thin pinecone looking cone a month or two ago? Second thing, if you have the basket, it is probably still on the plant, right?
If the cluster is on there it is an energy situation and has to do with the starch content in the stem. Answer back, and we can get you the answer you need.

Thanks, cycadjungle. The middle is a very large clump, as wide as it is tall, so I guess it's more of a basket than a pine cone. And, yes, it's still there. In fact, two weeks ago, one thin branch popped through the top of the basket, and I was hopeful that the sago was about to get well. However, since that brach popped out (and it's still there), the existing leaves are more yellow than ever. Any advice you can give me will be greatly appreciated.

Ok, unless you have a serious rot problem in the stem or roots, I can tell you what to do. First I guess, try to move the stem a little to see if the whole thing is firm, which might be a way to see if the plant is rotting. Given that everything seems ok, what I would do is carefully remove the cluster (I'll may call it a cone for now on, but it really isn't)The cone is made up of maybe 30 or 40 sporaphylls which each are attached to the apex of them stem. Carefully cut each one off starting from the outside working in and making sure that they are cleanly cut and not ripped off, because that can cause a fungus in the apex. After that, I would use a good fertilizer that has some fast reacting nitrogen and minor elements, and water it in real good. That will get some of the energy back into the stem. About a week or so after that, even though you may have found a fertilizer with a decent minor element package I would mix 4 parts Manganese Sulphate and 1 part Iron Sulphate and put down about 12 tablespoons of that mixture around the root area and water that in. The next flush should come out looking normal and green, which hopefully, you can get it to do by the end of the season.

DON'T REMOVE THE CLUSTER!!!!!! That wiil make seeds soon!! Just give HER some fertilizer! She should get threw this then.

"DON'T REMOVE THE CLUSTER!!!!!! That wiil make seeds soon!! Just give HER some fertilizer! She should get threw this then "

Maybe it has a bunch of seeds and maybe it doesn't. We haven't been told if there are seeds or not. Sometimes when we answer these kinds of questions we have to assume certain things if not given enough information. Usually, if new leaves are trying to come through the cluster then there aren't that many seeds. Also, I have to try and estimate how bad off this plant is and if it is good enough to leave alone or do something drastic and to me, if new leaves are coming out, and they look bad doing it, maybe the plant might not make it to breed again. Also, if kept properly, even though it is typically too early to remove seeds, they can be kept and can still spout next season because the embryos will stil continue to grow even if they are separated from the mother plant.