Unfixable blank page

Hello everyone !

I’ve been running a WordPress website for a few weeks with everything working fine. Since I’m just adding posts before launch, I didn’t look at the home page very often, but I noticed today that this page and every other public page (previews, categories, …) are blank. This may be caused by the WordPress 4 upgrade I did a little while ago.
I tried every fix available; disabled the plugins, set the theme to default, tried to enter debug mode, … Nothing worked. The only thing that gives me back those pages is to empty the database.

Any idea of what in the database could be causing this problem ?

Thank you for your help !
Alix