This means exactly nothing. It will happen every time and have no effect on anything. When it says "bounce: 1/1 sample: 1/1", that's what you're looking for. That should mean your cubemaps are built. Usually at that point I exit the map, type mat_specular 1 in the console (assuming you set it to 0 before building cubemaps) and load a different map, any map, then reload your map. Cubemaps should be in place and your shiny stuff should be reflecting the cubemap. If you don't load a different map first it may not load up your new cubemaps that you just built. But, it will pretty much always give you the error about the subdirectory and building the default cubemap. These errors are errors themselves, just ignore them.