Quote Originally Posted by Throbert McGee View Post
1. У вас есть сыр? (nominative) -- "Do you have cheese?"
2. У вас есть сыра? (partitive genitive) -- "Do you have some cheese?"
3. У вас есть сыру? -- Same as #2, but possibly can sound more "folksy" -- "Do y'all got any cheese?"

Therefore, in У вас есть сыру и мяса?, both nouns are genitive: "Do you have some cheese and some meat?"
It's a pity, but that's not Russian actually, save for the first sentence.

1. У вас есть сыр? ОК
2. У вас есть немного сыра? (= some cheese)
3. У вас есть сыру? incorrect (even for the rednecks)

I think you are a bit confused because you mixed up negative and affirmative forms.

1. У вас нет сыр? incorrect
2. У вас нет сыра? ОК
3. У вас нет сыру? incorrect (but can be acceptable for the rednecks)

I'm sorry that I broke your theory.