half of the faces gone in object mode

I just started modelling with blender and started out with the tutorials which are on wikibooks. I finished the tutorials on landscape modelling and now I want to model a cello with reference photos (because I play cello myself). I added a mirror modifier so that I only have to do half the work :D. I am quite happy with the outline of the corpus ( I still have to do the thickness) but when I went into object mode half the faces were gone!! (see the Images to understand what I mean) I turned off the mirror modifier and the subsurf modifier but that didn’t help, though the rendering pictures are fine in either case.

I hope you can help me!!



You might try Recalculate normals with Ctrl N. Maybe that will work.

Heres a good link to read up on them.

I had actually already done that but when I now i dit it again and it works.