I'm using the updated version of Carbonite on Win 7 with 4.01 WoW. No matter what settings I choose, how many times I reload my UI, I cannot get any waypoint arrow to work for me. Before 4.01 I had a nice little arrow that pointed me in the direction to go for the closest quest. Now, arrows don't show up. I've tried Questhelper, Tomtom, Carbonite, and nothing works. The arrow doesn't show on any characters.
TomTom clashes with Carbonites waypoint arrow if I remember right. Maybe try asking in the Carbonite forum section. Maybe someone else has also encountered your problem and can help.