I upgraded from setup wizard from 2.0.6. I can get to system upgrade and system config. I've tried with cache disabled and enabled.
i had the same issue, after lots of google search i concluded that, its file permission issue at my hosted server. while checking in the developer console in the chrome browser i found that some files are requested from "VENDOR" folder, i tried to give permission as per Magento guidelines but didn't work. than i tired 777 permission to "VENDOR" folder and files inside that folder and surprisingly it worked for me.
May be you can try the same permission and once you are done with our work you can revert back to standard permission as per Magento guidelines.