cursor is not correctly displayed in main menu or in skill/inventory screen

when in window mode (as opposed to fullscreen mode), entering the main menu or the skill/inventory screen or during dialogues, the cursor is not correctly displayed, it is just a random set of color pixels.

(RM-885 from redmine: created on 2013-08-14 by Yann GOUY, , closed on 2013-12-07 by nobody)