Finally the server is fixed. Everything should be working now without a security error. My previous host terminated my account without much notice because a few nethack process were stuck in a infinite loop or something. Now it's running on AWS which should be much better. Unfortunately because of an architecture change save files are not compatible with the new server so you might receive a notice about not being able to open your save file but everything else should be working and the score list was preserved. Send a bug report if you notice any other issues.
Things should be back up and working now, sorry for the downtime, I recently upgraded the server and neglected to setup the flash security file. Everything should work faster now, Submit a bug report if you encounter any problems.
I'll look into a little more later but if you get the security error or "Flash Nethack Loading!!!" or it just seems stuck. Refresh the game and try again. It shouldn't take but a few seconds to load so it it gets stuck just try again.
I think I got he security error figured out. Let me know if you are still getting it.
SavageWolf I think you are getting that message because the name was already taken.
I'll be working on integrating the login system with Kongregate so this won't be an issue in the future.
 "Flash NetHack"){kind=icon}