Annoying authentication window using IcedTea with Tor

[flo.xfce at gmx-topmail.de]

Hey,
I am running icedtea-web 1.6.1 in Firefox. Firefox is configured to
connect via Tor. When I am running a Java Applet I always get
authentication windows stating: "The web server at 127.0.0.1 is
requesting authentication. It says 'SOCKS authentication' Username/Pasword"
This message pops up more than frequently, sometimes every 10 seconds.
I tried different settings for IcedTea: Use direct connection, use
Browser settings, Manual settings; nothing changes the behaviour.
Apart from the annoying part this behaviour sometimes crashes my system.
In rare cases, when I raise another window in that moment when the
message appears, all applications freeze.
So how can I disable this behaviour?

Kind regards