One thing you could try is using the tightvncserver package on your RPi and Chicken-of-the-VNC on your Mac, it works pretty well for me.

Check out http://www.skpang.co.uk/blog/archives/398 for some installation details.

Jason

Berk, you could have a look at wicd this seems to work better for me.You can find out more about the package here http://packages.debian.org/sid/wicd