still only produces an empty text-box for me

.
Firefox 3.0.2 / flash 10 / java 1.6.0 (through new firewalled, NAT-router, updated -newest- firmware)
No firewalls on the server itself.
Only thing I'd be tempted to think is that Ubuntu have buggered about with Firefox's (or iceweasel's) source code a little and managed to bungle a work around.
Or perhaps you have a special plugin?