Can't smooth out correctly a PolySurface, please help.

Hi,
I faced a simple but strange problem which I am unable to solve on my own.I have already tried everything. I started to model my iPhone 3G, everything went ok, until I wanted to smooth the model as the final step before texturing.

Tried to add more divisions ("level 1"), and smoothing it via Mesh>smooth or via Proxy>Subdiv Proxy...and I get all kind of odd lines in my model.

Please if someone could tell me what am I doing wrong, so I could avoid it in the future??



Regards!!!