laptop's attached screen resolution.

[Hugh Sasse]

I'm using a Toshiba ["satellite pro"?] laptop plugged into an LCD
monitor.  When I boot I see the Kubuntu logo plus the progress bar
in the middle of the screen.  Then the screen goes blank, and I get
the login screen.  Unlike on the laptop itself, this appears
stretched so that the boxes for the username and password are just
off the bottom of the screen, towards the right hand side.  This
would appear to be due to some bizarre definition of the screen
resolution, which gets set when the login screen appears.  Also, my
screen is shared between the laptop and a Windows box using a KVM
switch [made in China, but whose manufacturers seem to be too shy to
say who they are or put a definitive model number on it], and for
just under half a second I see the whole screen when I switch to the
laptop, then it snaps to the "stretched display".  

http://ubuntuforums.org/showpost.php?p=129379&postcount=21

suggests that ctrl-alt-plus_on_numeric_pad should switch my resolution
but nothing happens.  Remember, I have not logged in at this stage.
The reason I'm using a separate monitor is to ease the pain of viewing
the laptop screen with my eyesight, so if I can get this to work by 
some key combination before logging in and meddling with /etc/X11/xorg.conf
I'd prefer that.
  
My monitor is a iiyama AU4831D 19" TFT LCD  monitor with max
resulutin 1600*1200 which claims to be plug and play for Windows
95/98/Me/2000, if that's any help.

Does this sort of thing sound familiar to anyone, and are there
particularly relevant docs I should read?  Whilst I've used various
flavours of Unix, mostly Solaris, for years, I'm relatively new to
GNU/Linux and its conventions.

        Thank you,
        Hugh