weird pango layout problem

[Liquid <liquid kuht it>]

hi,

sorry for the cross posting with pygtk ML but there I had no answer so
someone advise me to post here.

I'm playing with pango layout, I have now this verySimpleThing that
shows the line number aside of the textview area.

The problem appear when you scroll up or down the window, all the
numbers into the pango layout are unreadable as you can see here:

http://www.parafernalia.org/liquid/pango_strange.png

and the code is here, if someone likes to try.

http://www.parafernalia.org/liquid/pango_layout.py

Maybe someone had the same problem? Any hint is really welcome :)

thanks in advance, cheers
*L*