Yes, that's the line where the actual depth buffer size is stored for later comparisons. Since 800 is not power-of-two there shouldn't be any problem due to this bug, so I guess it's a different one
Could you please run the app through the debugger, with DX settings changed to debug as well? Just choose the dx-debug version, start your app from MSVC in debug and check where the program encounters a dx problem (enable stop at first dx problem in dx settings as well).