Comment 2 for bug 278485

The workaround I currently use when being connected to my 3g connection and another one at the same time is to replace the default route through the command line:

sudo route add default gw `ip addr show ppp0 | grep inet | head -n 1 | awk '{print $2}' | sed -r 's/\/.*//'` ppp0

Then, as long as I have my 3g providers DNS servers specified in /etc/resolv.conf, I can connect as usual, share my internet connection through Firestarter etc.