Wrong screen resolution on startup, need to restart

[John Talbut <john@dpets.demon.co.uk>]

When I start my computer I usually get a screen with the wrong 
resolution and not centred on the monitor, like this: 
http://lh3.ggpht.com/_aTSyvLB4YWc/SRFI4A9dk2I/AAAAAAAAABM/40kB7pOjaz0/Start%20screen.jpeg 
(without the moiré effect).

If I restart my computer I then get the correct screen.

Anyone know what is going on here? It only seems to have been happening 
in recent weeks (I am using Lenny and I keep it up to date).