Sorry if this is the wrong place but I am lost. I upgraded my Mac to Sierra (10.12.2) and Jabref starts (3.8.1) but apart from quitting and editing preferences I can do nothing. No menus, no windows. Totally broken. It looks like people have met some problems with Sierra but nothing like this one. Possibly not a bug from JabRef that is why I post here and hope to get some advice about what to do to try to solve this issue!