Yesterday mine stopped saving the weights. I can enter yesterday's and today's weights; tell it "I'm feeling healthy"; it generates the chart; and the next time igoogle refreshes, it forgets the most recent weights.
Mine is doing the same thing. It's been four days for me. I emailed where it said to email comments yesterday, so maybe they're looking at it. Who knows. It's only one of 4 places I graph my daily weight. I think I may need a hobby.