After nothing but sheer frustration and wasted time with indexing failures and having tried everything that has been suggested, I am abandoning Logos 4 for the time being. When it ceases to be a Beta in disguise I may return. I'll give it a good year, then I might even be able to install it on my iMac as well as my PC.
I understand that it was a complete break from what had gone before, but I never had any problems previously. Older versions never caused me any problem. Logos 1.6 was a revelation in 1993/4; Logos 2 began to open up the notion of real interactive Bible study; Logos 3 was a step change and I achieved things in Bible study and academic work I could not have imagined. With none of these did I encounter the slightest problem with the programs. Logos 4 sucks.
It's unstable, arcane and the searches are too large. Having a squillion results only swamps me. I sure hope I can turn off indexing when I come back! 
Every blessing
Alan Macgregor
(Banff, Scotland)