the expanded expander is misdrawn. It looks as if the triangle is not exactly symmetric, causing some ugly aliasing. This is rumoured to be related to floating point changes in gcc 3.4.1...
This really seems to be a compiler issue. Inserting any function call - even g_free (NULL) - between create_affine() and the loop over the points in gtk_default_draw_expander() fixes it.
Created attachment 103456 [details] proposed workaround