Perhaps this is already well known:
In LyX 1.0.3pre4 the preamble window behaves strangely if you enlarge it
and you have so much text in it so the scroll bars are present.
If you enlarge the window horizontally, the scroll bar on the right-hand
side goes really freaky.
If you enlarge it vertically, the bottom scroll bar behaves strangely,
and if you enlarge it so that it reaches over to another screen, and
then decrease it back to the first screen, LyX seems to crash and quit.
The same happens if you decrease the window sufficiently much
horizontally.
/Alex
