I had a working install of LibreOffice 4.x. I first tried to upgrade to the LibreOffice 5.x 64-bit version. That hanged on startup of any of the LibreOffice applications (I get a splash screen and nothing else). I uninstalled the 64-bit version and tried installing the 32-bit version. Same thing happens. I tried deleting the %AppData%/LibreOffice folder. Anyone have any ideas on how to fix? Or know where I can download the 4.x version as it was working before I upgraded? The libreoffice.org site only seems to offer two 5.x versions and the 6.0 beta.
You could try safe mode; if that fails, there’s Index of /libreoffice/old for you 
Btw: you should not think about 4.x vs. 5.x; 4.4 has ~the same amount of differences with 5.0 as 5.0 vs. 5.1; actually it doesn’t matter if first or second part of version changes - they are all major releases. Only third part means minor change. So, you should tell which version failed for you more precisely.