Nvidia driver problem on Ubuntu 14.04.1

On a freshly setup Ubuntu 14.04.1 64 bit on my laptop(GeForce 840m) I had tried setting up Cuda 6.5 via the debian package given at https://developer.nvidia.com/cuda-downloads#linux leading to the error on running

cuda driver version is insufficient for cuda runtime version

Following this after reading a few forums I downloaded and ran the .run file in the same link above.
Now although Cuda is working perfectly my Ubuntu desktop just does not show up after logging in showing only my default wallpaper. Ive tried resetting Unity,switching to Gnome,using compiz manager and a number of other proposed solutions. Any suggestions as to what I should do now?