i also got yellow light all the time ...
tried forwarding triggering and all the shit but didnt really succeed
until i started playin around with the portrange in the prefs
so for one machine behind a nat i got it to work with just entering
192.168.x.y:6881 and 6881 as public port using the virtual server
if u want to use serveral instances of ur clientapp u gotta add some
more ports like 192.168.x.y:6882 ... 6883 .. and so on
but remember to adjust the portrange in the prefs and save it
for more than one machine i would try to set a port triggering only
or use a different portrange for each machine like
192.168.x.y:6881-6885 for machine1
192.168.x.z:6886-6889 for machine2
and again: set the portrange in the clientapp !!!
to check if a port is open or not i used shieldsup at grc.com
all u need to do is enter the portrange eg. 6881-6889 and
pray that as many ports are open as btclients are running at
so if no client is active at all the ports must be closed or maybe stealth
have fun