Hi:
To isolate the problem I tried with another distro with the same host configuration(qemu files, host W2K behind ISA proxy). Opened firefox browser and set manual proxy xx.xx.xx.xx:8080 , after that firefox pop up a user/pass windows to authenticate and can browse the net!
May be is an opera browser issue or a wrong configuration of the interface eth0 in TC, I will download firexof in TC and give it a try.
wget don't work, I need to explore a little more.
regards,
alex