I have just upgraded from 9.1.0 to 9.1.1 using Owncloud's Debian 7 repository. Everything went smoothly. However, the calendar app no longer shows calendar entries. I instead see a blank calendar and spinners appear under "New Calendar" and "New Subscription". Subsequently, the task app is just a blank white page with the Owncloud header on top. This happens with the latest Pale Moon 26.4.1, but not with Firefox 45.4.0, both on Linux.
There are no errors in the web server error log.