Created attachment 130413 [details] after setting freeze in A3 but before sortting If the "Freeze rows and columns" has been set through the icon (which is supremely stupid move to remove this function from the Window menu item) to cell A3, that should limit a sort to a range beginning with row 3. The current option in Sort that "Range contains column labels" assumes that only row 1 contains those labels and will include row 2 in the sort.
Created attachment 130414 [details] After sorting row 2 which was frozen is included in sorted rows
As I have tested the option it's on the Menu/Edit/Freeze cells. It's the first time that I have seen a request like this, and now every think that people like can be incorporated. If you want that, then select the range to sort that you like. You can define a database range, that can be easily selectable to sort.