contextmenu pass screen border

["transnet gmx de" <transnet gmx de>]

Hello all,
 Excuse my poor English.
My Problem is that in an Gtk++ application, the enties of a contextmenu
pass the screen border, with the effect that I can not reach them. It
can be that this is a trivial, yet hundred times treated theme, but,
probably due to my missing vocabulary, I cannot find the solution, so I
stick to the problem. 
Thanks
Thomas Feldburg

My System: Debian, Woody, monitor resolution: 800x600 I guess,gtk++ 1.2
and 2.0