I received the message “Class not registered” as well, but did not catch the rest of the message. It occurred after first time running “ionic start myproject” after doing npm install of ionic and cordova on Windows 8.1 Pro.
Hi. I don’t know if you have been able to find a way to solve this issue yet but I also had the same problem running the ionic serve command in windows 8.
However the solution I found for now that is working for me is to run the ionic serve command and then after the error shows up, I open a new tab in my chrome browser and type in the localhost address directly (localhost:8100) and hit enter. For some reason this works for me cause from the npm cmd you see that the server is actually running.