Mac or Win?
I have had this happen with later versions of LR CC after a crash. All kind of things can go wrong and LR seems to crash more often for me.
I would also try resetting all your preferences, deleting the cache again. Also try importing a new image, as a test and see if you get the same problem. You can also backup the catalog, then move it to a new location and then point LR to that location and see if the problem persists.
Worst case, you may need to remove it all together and re-install the program.
Paul C