It means you have shorted those nets together somewhere on the schematic. 
Apparently you have already been searching for that. Have you used the highlight tool?
a relatively common mistake is to short the +5V and GND nets right through a decoupling capacitor.
Also, thing like this:
are never good. Wherever you see either small red circles (open pins) or small green crosses (open wire ends) are suspicious. Just like the junction dots on places where there should not be any junction dots.
And if you still can’t find it, then zip up your project and post it here. I can probably spot it in a few minutes. But before you can upload zip files: