From the first entry under troubleshooting via Nas wiki:
http://nasomi.com/wiki/index.php?title= ... charactersPassword entry causes double-entering of characters
Cause: A recent windows update. If you have more information regarding the exact cause, visit NasChat.
Fix: Open the Nasomi launcher. Right click the configuration you want to launch. Click edit. In the "Command" box, add --user yourusername --pass yourpassword. Do not delete anything from the Command box if it isn't empty!!! If you don't understand, here's a gif. If it asks you for your username/password afterwards, this means that the username/password you entered into --user or --pass is incorrect