I have the same error.
To fix it do this:
*When you press F5 you will get that, press F5 again to get back on editor, F5 again for test.
*To disable that windows, press t for chat, and click the "Ok" with an arrow
*"*"You are done.
But in my case, i can go back.You could try doing a windows back up of your system.(ofc, back up the configuration you are using now.)
*--Or try rebooting the pc, that usually works
*---Or, you could try updating your server to 1.0.4 or 1.0.2 (1.0.3 not included due alot of errors to others)