LR6 hanging on opening.

I have just purchased LR6 and installed it on my windows pc. PC is windows 7 operating system with 64bit graphics. LR hangs when opening. I have installed latest version of the graphics processor, un-installed and re-installed LR 5 times. It will not get past the picture with trees......I have wasted 4 hours on forums trying various other things from library to re-installs. Please can you help.