In order to display graphics smoothly, YASARA should redraw the screen synchronously with your monitor, otherwise you may encounter so called 'tearing effects'. Not all graphics cards allow you to activate this option.

In Windows try to go to Control Panel > Display > Settings > Advanced > OpenGL and see if there (or close by) is an option called 'Activate Sync to VBlank'.

In Linux, it depends on your graphics card. nVIDIA cards should be handled automatically by YASARA. Until 2006, ATI Radeon drivers allowed you to activate this option during the installation. Nowadays you can simply run as root 'aticonfig --sync-vsync=on' and then restart the X-server. Unfortunately this does not always work.

In MacOSX, YASARA normally activates the synchronization automatically. If you nevertheless get the warning, it points towards an internal MacOSX problem.