I've been running the native resolution of my laptop LCD (1920x1080) with no problems until 10.5 and 10.6. With 10.5 or 10.6 the maximum resolution I can change to is something like 1440x900. xrandr doesn't show any resolutions any larger than that either. The same is true of my external LCD on HDMI (2048x1152) if I plug it in. Going back to 10.4 works fine and I can change to all resolutions supported by either monitor.

Any ideas? I'd really appreciate it.

My system: ATI HD3650, Gentoo x86-64, gentoo kernel 2.6.27-r6, xorg server 1.7.6, xorg x11 7.4-r1, xfce4 4.6.1, lib/xrandr 1.3.2