Yep. That's crappily bizzare.
Be sure to file a bug about it so the developers know.
Check out the /etc/X11/xorg.conf file and make sure that the correct settings are there for your monitor.
You can probably get to it by going ctrl-alt-F1
Then logging in.
The file is divided up into sections. The important section here is the 'monitor' section.
This is what I use:
Section "Monitor"
Identifier "Generic Monitor"
Option "DPMS"
EndSection
That's the most 'correct' way to do it. This way it's dynamicaly configured from teh DDC values the monitors use themselves. Doesn't always work though.
Also if you want to manually put in the range of horizontal and vertical syncs you can add these lines to that section:
HorizSync 31.5 - 48.5
VertRefresh 60.0 - 60.0
Of course edit the values to match your monitor.
Eventually it will look something like this:
Section "Monitor"
Identifier "Built-in LCD"
HorizSync 31.5 - 48.5
VertRefresh 60.0 - 60.0
EndSection
Since your dapper install works you can probably just copy the configuration, or at least the monitor section from that....
sometimes people like to add 'modelines' settings for LCD displays.
These are a throw-back to ancient XFree86 3.x days.. they allow a high degree of control though.
If you have modelines present in your xorg.conf and they aren't working then delete them.
Realy I don't know why on earth people use them. They are only needed rarely. Sometimes they can provide a better picture quality or something like that, but if they are causing issues then get rid of them.
Also before editing files make a copy of them.
So if you edit something and it makes it worse or you have a typo you can't figure out then you can copy the old one back over the new one and undo any changes.
However since this is a live cdrom then it'll just get regenerated each time you reboot so it's not a big deal.
edit:
Oh, the 'identifier' line is important because it's used to reference that monitor section in other parts of the configuration.