It appears that the Nutro problems are more widespread and separate from the melamine scare of last year. In addition to Debbie's link, here's another link to more recent problems with Nutro's foods:
VoyForums: Nutro Natural Choice Dog Food Recall Message Board
I had my rottweiler on Nutro Natural his whole life, as it was one of the only foods without any ingredients he tested positive for allergies. He died last summer with torsion/bloat. I hope the Nutro didn't kill him.