I’ve installed a new version of SimpleServer for NGminecraft’s servers. I haven’t replaced the maps yet but will be uploading the download links in the near future.
I have had errors stating “The server responded with an invalid server key” and would not be connectible for about 15 seconds. Simply wait 15-20 seconds and reconnect. If you’re still having issues, drop me a line at ginbot86 [at] gmail [dot] com.