Since a few days, when I open a fresh Mathematica 10.4.0, start a new document and start typing 'Q' (from Query). It will load the autocompletion list, but fails at it and crashes Mathematica. Even repeating it over and over, very reproducible.
I have now switched off the suggestions, but they are very nice to have... Are these definitions stored somewhere, and could they be updated in the background somehow? It works flawlessly before... Can I reset it somehow?
Mac OSX, everything up to date.
