I've caught at least a couple of Mathematica bugs over the years -- google seems to confirm that they're not very unusual. I haven't seen *this* one, but I haven't dealt with Hermite polynomials in a long time. I have noticed based on my own experience and other's reports that Wolfram is not particularly good about rapid fixes, which is bothersome given that so many people depend on Mathematica for their research and could be seriously led astray by defects. Anyway, there's a Mathematica "Stack Exchange" site, and I suggest asking there about whether others have observed the behavior. They even maintain a category of confirmed bugs...