This took me AGES to debug, but I finally found what’s causing this:
problem:
unable to connect to repository in Krypton (all beta’s)
logfile says: failed read ‘http://mirrors.kodi.tv/addons/krypton/addons.xml.gz.md5’
I had to remove these caching settings from my advancedsettings.xml file, and then the repositories started working again !
<cache>
<memorysize>0</memorysize>
<buffermode>3</buffermode>
<readfactor>0</readfactor>
</cache>