Don't know if this is of interest to anyone, or if it's been posted before,
but I thought I'd post it anyway. :)

In the level "Urban Flight," you come to a section where you drop down into
a walled off "arena" and face an antlion queen. Being the chicken that I am,
I tried to find a way to avoid having to fight, but the queen only appears
once you drop down into its area.

So after dropping down I piled three crates on top of one another, and
jumped back to the place I had dropped from. Alyx was still standing there
waiting. The moment you turn so that Alyx if off-screen, she magically
teleports to another platform outside the door. Handy (especially as there's
an invisible wall there that stops me jumping on to the same platform --  
grrr).

A few seconds later, the game crashes to the desktop. I've tried this three
times now and it did it every time.

Oh well, guess I'd better stop being a wimp and fight that antlion myself!