If you can compile CHDK, try removing / commenting
#define CAM_SHOW_OSD_IN_SHOOT_MENU 1from platform/sx50hs/platform_camera.h
I tried this suggestion. It works with the ISO, exposure adjustment and FUNC/SET menus but not the others. Better than it was I guess. What I've noticed though is all the menus where it doesn't work are transparent and disappear after some time. The ones that have some opaque elements which don't disappear now seem to work correctly.
