Doing any of the following causes a crash for me. Oddly, it doesn't usually crash right away, but invariably crashes at some point later in the same session.
- Previewing imagespacemodifiers and scrolling away from one before it's done animating
- Editing shader effects, at all
- Editing particle effects, particularly swapping out textures
- Opening more than one of any single type of window at once (i.e. two magic effects, two quests, etc). This also causes glitches while both are open, such as one magic effect's settings getting wiped empty if both are changed and saved.
And, of course, CK will just randomly be gone sometimes after I run Skyrim to test a change.
Of course, I have also run fairly active sessions for 5 hours or more without a single hiccup, so it's not all bad. If I do anything on the list above, I generally just save right after, then relaunch the CK and keep going.