I'm using InDesign 16.1 x64 on a Windows platform with intel i7 quad processor, 16GB of RAM, plenty of hard disk space, etc. I've created a 487 page document with only one master page for a book so it's a simple document. I'm not using Layers.
On page 463, at the beginning of the page, the cursor appears with its characteristic blinking on and off. At any point thereafter I cannot click to insert a Text cursor. I can click, but nothing happens. No blinking Text cursor at any x,y position thereafter. It's like the cursor is stuck at the beginning of the page.
I've re-booted, saved document with a different filename, exited InDesign and opened it again. Nothing works. It's almost as if the program has run out of memory with too many pages.