The white screens, etc. are almost certainly the OpenGL/OpenCL bug (Q64314) (however, that also affects 5.0.5, which is why I never wrote anything when I first saw this).
There are Release Notes for 5.1 but do not seem to be Release Notes exclusively for 5.1.1. However, there are detailed notes on 184.108.40.206, including bugfixes. tdf#97197, tdf#97739 & tdf#97816 are all OpenGL bugfixes. The OP will be particularly interested by:-
tdf#97197:- With OpenGL active Impress slide transition Rochade effect blanking entire UI to white [Michael Meeks]
In addition to the above are detailed notes on 220.127.116.11. I count 4 OpenGL/OpenCL bugfixes amongst a terrifyingly long list of fixed errors.
In v5.1 use of OpenGL/OpenCL defaulted to ON, and this was responsible for a wonderful set of show-stopping bugs such as your own. This has all led to the ludicrous situation where the current (March 2016) Release Notes for 5.0.5 include a fix for crashes on startup:-
In case of problems on Windows related to OpenGL rendering, you can disable it completely by applying a registry setting (only needed if LibreOffice crashes on startup, otherwise you can disable it in Tools|Options → LibreOffice → View). You can find the necessary fragment in bugzilla (save with a .reg file extension, then you can double-click on the file to apply the change).
To understand why the I describe the above as “ludicrous”, here is LibreOffice’s self-description of Still:-
LibreOffice Still is the stable version that has undergone more testing (over a longer time).
It is usually recommended for more conservative use.
The fact that a so-called ‘stable’, ‘well-tested’ product is very likely to crash on first start-up defeats my mind.
I’m very pleased that GAJ was eventually able to get an updated product that would run without a crash‘n’burn.