X root cursor changing randomly?

[Tom Horsley]

Just curiosity: Has anyone else noticed their root X cursor
randomly reverting back to the default big hollow X shape?

I've got it set to an arrow shape, and at some point during
my session it will suddenly go back to the default X shape.

I can fix it with xsetroot, but I have no idea why it is
changing on me (and I haven't changed anything in my
session - just downloaded updates from time to time).

I can't imagine there is any way to track this down
that would be worth the effort, but I just thought
I'd ask if anyone else has seen it.