I just reset one of our sandbox instances to the 9.0 release this evening and I was reminded of one of the weird messages you might get trying to access your instance after the reset. In this case they moved the instance so it got new DNS entries. When this happens you will see something like the following :
Nice old logo and it still says CRM Online! I think they have forot this page exists :) Any way if you get this, there is no need to wait 24 hours, simply do a ipconfig /flushdns to clear your local cache, restart your browser and you should be good to go!