HELP! Yes, I got the unexpected error opening catalog after letting adobe update my lightroom.
Then I uninstalled lightroom, did a clean install of lightroom 6, updated to 6.8 and I still get this HELL message. It won't even open any of the backups of which I make one per session.
It's only my life work sitting in these catalogs - I so love the horror of Adobe updates. I'm on a iMac - Lat 2013, system 10.12.2.
It worked fine before the hell upgrade.
I was able to import original the catalog into a new one. That worked and the new catalog opened OK. Then found a problem with the disk the original catalog was on. I unmounted the disk then mounted it again and ran disk repair. The catalog open now... love those unknown errors. Whew!