I believe we can help you more if you upload the file.(even a part of your polygons)
In the mean time, I would suggest you try several attemps.
(You don't have to do them in order. The order is irrelevant to the possibility)
- Check the Normals
- Remove doubles
- Find a extra face or edge within your mesh
- Switch the Shading to flat
- Apply all modifiers if you have some
I will talk in them in detail.
1. Check the Normals
If trying "Recalculating" is the only thing you have done, try flipping the faces individulally. When you are in Edit mode, you can visualize the direction of the Normals in the [Properties Region] -> [Mesh Display] -> [Normals].
To filp a selected face, use the [Specials (W key)] ->[Filp Normals (F)]
2. Remove doubles
You might have several vertecies at the very same xyz coordinates. In this case, they can be removed by [Specials (W key)] ->[Remove Doubles (R)].
3. Find a extra face or edge within your mesh
You might be having an unwanted face like in the screen shot.
I don't know the best way to remove this but there are some tips.
- Hiding vetecies with the H key may help you find the unwanted face.
- The Subdivision Surface Modifier will be destorted around the extra face.
Note that this may happen with Edges too.
4. Switch the Shading to flat
The problem might be simply that the smooth shading seems unfamiliar. (Although I doubt it)
Set it to Flat.
See here for more details.
5. Apply all modifiers if you have some
Maybe the reason is caused by some complex computing by the Modifiers.
If you have some try Applying them for a while.
Please be careful not to exceed to far that you cannot redo before applying.
Hope it helps.