None of the little buttons that are on the dialog actually make the cross-fade go away. I have a similar problem with Fade Ins/Outs, but at least there I can do (what I think is a workaround) by typing in a fade length of "0.0’’ and then it goes away.
For crossfades, my C6.5 won’t even accept that - I have to manually spin the length of the fade down to 0.0 using my mousewheel!
I had a similar problem: crossfaded two events and when I took one away to a different track, the two-part somehow “bent” fade out curve remained but I wanted a linear curve again…