ARD fails to update remote screen image

[michaelsanford]

I'm using ARD 3.2-current to connect, over the internet and through two NATs, with holes, to another older iMac also running 3.2-current.

I've noticed an odd bug in Leopard (administration machine) that I did not experience with Tiger: the remote screen draws only once, never updates, until I change the colour depth of the display, then it redraws once.

Could I have an odd NAT problem? I can't imagine that I would, since it connects. Ports 22, 3282 (I believe, whatever is used by ARD) and 5900 are open on the client router.