Endnote X6 won't open my Endnote X4 library!

I had a library (large - about 15,000 references most with PDF attachments) and was using it with X4 without problem. I then upgraded to Mavericks, which required me to get X6, and when it ran for the first time, it “Indexed the PDFs” but then refused to open the library file - says cannot open it. Surely X6 is backwards compatible with X4 data; how do I get it to open the library?

Had a backup right?  – if not copy the current library and the .DATA folder to a new place, and then try to “recover library” from tools (at least that is where it is in the Windows version).  

If that doesn’t work, contact Tech Support.  Why X6 ?  – X7 has been out for over 2 yrs?  

Yep, had a backup. But new computer only runs Mavericks, so have on choice but to upgrade to Endnote X6 or X7 (was happy with X4), so I have to make it work somehow. I’ve tried the “Recover library” - same outcome. It supposedly recovered, but then won’t open and insists on re-indexing PDFs. X7 does the same thing.  Launched tech support ticket yesterday, haven’t heard back yet.

I would call if at all possible.  You usually get better support.