Keep getting message Sketchup not responding

[SketchUp3D_de]

SketchUp 2015 Not responding when saving model

this message is not created by SU but shown by the Windows Vista/7/8 Desktop Window Manager (DWM) after * iirc * 5 seconds if a programm is busy in doing something time consuming and therefore cannot respond to Windows events. You can check what’s going on by pressing Ctrl-Alt-Del and opening the Windows “Task Manager”, do not kill SU until saving/exporting/importing lasts aeons…

• what operating system?
• which SketchUp version?
• model size (“Window > Model Info > Statistics”)?
• hardware (CPU, GPU, RAM)?
• “Window > Preferences > OpenGL > Use Hardware Acceleration” on/off?