Network Manager don't seem to like other programs modifying DNS. There's a way to force it to work with barry.
I don't know how because I don't use network manager because I hate it. I use Wicd. I highly recommend you to use wicd.
"There is no reason anyone would want a computer in their home."
- Ken Olson, 1977
( And we now wear them! Blackberries are computers too! )