From Melchior Franz, "Attached is a fix for remaining problems in capslock handling:

It sets osgGA's keymask when restoring keys on FocusIn, according
to the state values of XKeyEvent and XCrossingEvent. (These are
the only source for X11's current capslock state that avoids
pulling in the XKB extension.)
"

include/osgViewer/api/X11/GraphicsWindowX11

@@ -166,6 +166,7 @@ class OSGVIEWER_EXPORT GraphicsWindowX11 : public osgViewer::GraphicsWindow
         void forceKey(int key, double time, bool state);
         void getModifierMap(char* keymap) const;
         int getModifierMask() const;
+        void syncCapsLock();
         
         bool            _valid;
         Display*        _display;