If this is any help to those of you with papers or a thesis that you need to get finished urgently, i have found a solution that might do until the problem gets sorted. I have just spent two days tearing my hair out after my thesis doc (last opened in June) suddenly started crashing whenever I tried to insert a new citation or do anything in the doc that involved communication with Endnote. I’m on a Mac using Word 2016 and Endnote x8, but it initially started happening on Word 2011 with Endnote 7.71. I copied the entire thesis (without unformatting citations) then pasted it in a fresh Word doc. Amazingly now it works, even after I have saved it and reopened the new doc. This is obviously a significant issue that Endnote needs to fix, but hope this helps someone in the meantime.