Newbie PROE g-code generation

Hi,

I'm a total newbie at CAM, and I'm using PROE wildfire 4. I managed to make a model, and in the machining mode I managed to create the NC sequence and it works just fine - I can see the virtual milling process with toolpaths and everything.

The problem is when I try to generate the G-code. I get an error regarding the RETRACTION PLANE? I have no idea what to do. I tried to change it, remove it, lower it, you name it - but nothing works.

PORE gives me this error:
FEATURE 13: MILLING NC Sequence cannot be created; check NC Sequence retraction plane

or this one:
FEATURE 14: MILLING NC Sequence cannot be created; check NC Sequence retraction plane

I have no idea what to do, any suggestions would be appreciated.

Thank you!