Check the [appdata]\modules folder, it should have a cms folder in it. If it didn't then something with the upgrade went wrong and you will have to go back to 7.0.
One common issue is that the filerights are not set correctly on the files affected by the upgrade. Check that the files are not write protected and not on a external/network folder which have special rights.
I upgraded my Website to from Episerver 7 to 7.1. After upgrading the edit window was totally blank. Well not totally I could see the colored edit bar, and everything that is rendered when it's expanded. Admin mode also worked. I followed the following solution
http://blog.nansen.com/2013/04/blank-edit-after-upgrading-to-episerver.html but it never worked. Any other solutions will be appreciated.