Quite recently (only within the last few days?) I've very frequently
seen emacs crash like the following:
1) create a new window with C-x 5 2
2) switch to the new window
3) try to give some emacs command in it -- and notice it doesn't
respond
4) switching back to the old window allows you to enter commands just
like normal, it's just the new window that ignores all inputs
5) deleting the new window will usually then make emacs crash shortly
(I usually make a new new window after that, but I'm not sure if
it's necessary)
6) sometimes it crashes directly at step 3