I am brazilian, and I can type à, û and etc perfectly in dia. Isn't it
your X11 configuration or LC_ALL environment? Is it dia specific or any
X or GTK application has the same problem?
I am using Windows environement not X11. So I guess there is some
problems in Windows version.
Anyway, you can get around it with cut and paste. Open gucharmap, select
the characters you want, copy it and past in dia (edit->past _text_).
Yes this will be a solution to that problem. But may there is something
better I can do ton cofigure Dia fonts in Windows.