First, try to reset the preferences: Hold down the Shift and the Alt key while starting LR (clicking on the executable) and see if this helps.
I seem to have made it worse by trying to open a new catalogue at the start. (Holding down ctrl whilst clicking on the exe).
I'm on windows 7.
LR version 2015.2 release
If resetting the preferences does not help, I suggest to roll back to 6.1.1. If you'd like to try LR, I'd strongly suggest this anyway to not get a wrong impression of LR
There are many confirmed issues with LR 6.2 - you may try the steps here: Update on Lightroom 2015.2 / Lightroom 6.2 Release
Anyhow, you are best helped if you roll back to 6.1.1 as many users: http://www.lightroomqueen.com/how-do-i-roll-back-to-lightroom-2015-1-1-or-lightroom-6-1-1/
There are hundreds of threads covering issues with 6.2 / 2015.2.
Still no joy . I think I'll rebuild my laptop it; it needed it anyway.