Thanks dtoub. Things are looking bad to those of us who (like you and me) have a long-term commitment to Endnote.
In parallel to this board, I have raised a case with technical support directly. Here is the lastest message I sent to them, sent about 90 minutes ago:
Just to note that your representative called me an hour or so ago.
He asked me to start Endnote X8, and run the customiser, with Word for Mac 2011 off, which I did.
Once the process was complete, he asked me to start Word for Mac 2011, which I did.
He asked me to check whether Endnote was showing under Tools; I told him that it was not.
He asked me to open the Templates and Add-ins option under the Tools menu, and check all the options in the window.
I did that. Endnote appeared in the Tools menu, but when I followed his instructions to select one of its options Word immediately crashed.
I told him that I had tried all this before, with exactly the same results. He was unable to propose any further options, and said he would try to reproduce the problem and call me back.
So far my problem remains unresolved.
I agree with you that unless this mess is fixed soon, things are looking very bad. And, as I said, I shall be asking for my money back on the grounds that the compatibility statement for Ennote X8, quoted in my earlier post, was seriously misleading.