Hi there!
I did a global search on the forum about this issue, couldn't find anything similar.
I have a fabric object that I want to have hair. Setup was pretty straighforward and renders also quite fast in the viewport (after 17 seconds it starts rendering - 2 hair objects, 700000 hairs in total).
The problem is that as soon as I want to render the image in the picture viewer, it hangs on the first stage 'preparing'. I've let it prepare for more than one hour, but doesn't do anything. It neither crashes, I'm still able to stop the render and quit the picture viewer.
Deleting the hair objects and inserting new hair objects with a lower hair count (initial - 5000 hairs) has the same problem. Renders fine in the viewport, nothing happens in the picture viewer.