I've just spent the last 2 hours debugging a networking issue with Gentoox thanks to the help of "jeytr", who allowed me to SSH into his Xbox. It turns out the networking option labelled "TCP: explicit congestion notification support" breaks outgoing TCP traffic for some users. If you find that you cannot connect to anything via TCP, you should do the following:

Login as root.

cd /usr/src/linux
make menuconfig

Go to "Networking Options ---> IP: TCP Explicit Congestion Notification Support" and disable this option by pressing 'n' on your keyboard. Exit the menuconfig system and choose to save the config.

make dep
make bzImage modules modules_install
cp arch/i386/boot/bzImage /mnt/fatx/e/vmlinuz
reboot

When your system boots up again, networking should work properly!