You must dereference the pointers, otherwise you are moving the address of the pointers and possibly corrupting other memory locations. Example

procedure TForm .Button Click(Sender: TObject);
var
  p  : pointer;
  p2 : pointer;
begin
  GetMem(p ,  28);
  GetMem(p2,  28);
 {This line may cause an access violation}
  Move(p , p2,  28);
 {This line is correct}
  Move(p ^, p2^,  28);
  FreeMem(p ,  28);
  FreeMem(p2,  28);
end;