In small nonstick saucepan combine sugar, syrup, and vinegar; stirring constantly, bring to a boil.
Reduce heat and let simmer for 2 minutes.
Add peanut butter and vanilla and stir to combine.
Place popcorn and peanuts in flameproof bowl and set over lowest possible heat; add peanut butter mixture and toss until popcorn and peanuts are evenly coated.
Moisten hands with cold water, then shape mixture into 4 equal balls; let cool before serving.