Acrobat no longer opening files with macOS High Sierra / Security Update

Recently I updated to Security Update 2018-001 on MacOS High Sierra 10.13.4 - since then, none of my Acrobat instances (DC Pro, X) works anymore: I can start Acrobat, but as soon a I try to open a file, Acrobat hangs (showing the "rolling ball") and I have to force quit. Deinstallation and re-installation did not solve the problem.

Resolution is urgent since we depend on Acrobat for our internal processes.

Message was edited by: Peter Janes - description clarified after further analysis