Why do you think there's a problem with second.y? You create an instance of Second, but that instance is never used anywhere.
To find out where your error about invalid textures comes from (you should really copy error messages verbatim, not paraphrase them), you should check every SDL call you make. Currently, you seem to almost 10 SDL calls before your first SDL_GetError() call.
Basically, check the return values and see the first point it tells you something's wrong.
Also, this is a small enough program that I would definitely recommend you learning how to use a debugger (setting breakpoints, looking at variables and seeing the flow through your code, etc), if you don't already know how.