TurboTax is not misbehaving. Your broker might be misbehaving, or you might be misunderstanding the 1099 that you got from the broker). Exactly what kind of "investment gain" did you have? Capital gains from the sale of stock or other investments is supposed to be reported on Form 1099-B, not 1099-MISC. Dividends an interest are reported on Form 1099-DIV or 1099-INT respectively. Did you have a gain from some unusual type of investment? Which box of the 1099-MISC is the investment gain shown in?
