The SSL cert for sabnzbd is invalid by default as it's self-signed. You need to open the site in Firefox first and a security warning will be shown. Add an exception for the site and then add your connection details to NZB Unity and it should work fine.
Basically useless when authentication is necessary. The gui is also not the best either. I might switch back to chrome for nzbget-chrome... REPLY: I think the main missing gui feature (I know it involves more than just the gui) would be to be able to add nzb files straight to my nzbget with a button click. On the Chrome nzb plug-in this makes my life so much easier.