iMac LCD resolution

[Jim Cheetham]

I installed Warty on my iMac flatscreen machine, but I have problems
with the display resolution.

Using dpkg-reconfigure xserver-xfree86 (or dexconf) I've asked for
1440x900 as default (with the nv driver).

However, when I start gdm, I get 640x480 ...

After a bit of fiddling and re-running, dpkg-reconfigure has stopped
asking me what resolution I want any more (I'd edited the
XFree86Config-4 by hand, but later deleted it and rerun dexconf to
regenerate, as well as apt-get --reinstall xserver-xfree86), although
the config file still lists 1440x900 ... but when X starts I get
1152xwhatever, quite useable, but not all of my screen :-(

Any suggestions for resetting things to the 'correct' resolution?

(And there's no chance of dual-screen support at the moment, is there?
iMacs aren't supposed to support it (mirroring only) but it's an easy
Open Firmware preference to get OSX to run dual-screen ...)

-jim