There seems to be some strange behaviour with dual monitors.

I have a 27" iMac (2560x1440) and I have an external monitor hooked up (1920x1200) and positioned to the right of the main desktop.

When I move the cursor around on the second monitor, the picker preview window stops tracking and updating when I move close to the top edge (maybe 100 pixels?) or the right (farthest) edge (at least 300 pixels there) of the monitor.

edit: I'm running Snow Leopard 10.6.8