Ive got a subdivied cube here, I split it into 2 vertex groups, made two NURB curves then applied them to their representive vertex groups, basicly I want my cube to bow in on both sides, all the names are set up right… but I get a REALLY messed up shape, heres a picture, its supposed to be a magnet, yeah… obvisaly it needs more work.
http://img167.imageshack.us/img167/6585/omfgwtfbbqmagnetbn9.jpg
i dont understand. when you say you “applied” the nurbs curves to the mesh, what do you mean exactly? What did you press or click in Blender to associate the curve to the vertex group?
I don’t know if this will help you or not but here are some notes I took a while back when trying to figure out how to may a path extruded shape. At the end of the notes is possibly what you are having problems with. Sorry I didn’t answer sooner but I couldn’t remember where these were and I’m still not sure it’s what you are trying to do. Maybe some help.
- Start with the default scene and delete the cube.
- Make sure you’re in top view and add a Bezier Curve.
- Go into Object mode and switch to side view.
- Add a Bezier Circle and scale it quite small (the diameter of your pipe). This will be your profile.
- Go out of Edit mode and select the curve again.
- Go to the Edit buttons. There you’ll find an input box “BevOb”. Type in “CurveCircle”; the name of the bezier circle.
There is a more simple way to do this:
Create your hose (tube) in a straight line. Make sure that it will be long enough for the use you want, when it will be bent.
The mesh must have a sufficient number of extruded raws of vertices, in order to bend smoothly.
Make a Bezier curve ; this curve may be already with the final shape, or as well in a straight line.
Make the curve parent of the hose mesh by CTRL+P, and chose Curve Deform in the parent options.
The hose mesh is “aspirated” by the curve.
Move the mesh to have no weird deformation, and now you can adjust your curve as needed.
As I remember this technique was finicky. I think there were some possible fixes posted today even in CVS, but again not entirely sure.
An easer method might be to use Proportional Editing. In front view subdivide you cube a few times select the band of verts through the middle. Turn on Proportional Editing set falloff to sphere. Scale on on the x axis and you should get the results you described.
Thanks ReeVee, that got it perfectly.
For roger, I was apply them under the objct modifers - curve deform place, its in the same list as subdivision surfaces. Ill test thats sometime Marty, but I killed my curves a little while ago so I can’t test it right now.
bah, ignore me. I’m just talking. 
Rereading your post, and listening to ReeVee, another way to achieve what you’re looking to do could be with a deformation lattice. Then after you have the shape you want you just apply the lattice.
Proportional edit would probably be the way I’d do it too though.
