Failed to Create all the graphics for the NavBar.......

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I am using the Webstyle4, and as I would like to save the pictures of NavBar, it would jump a window to inform me that:
Failed to create all the graphics for the NavBar such as preview66b1, etc...... (as attached)
Is anyone have faced the same problems? Pls help me on this matter, and advise us how to solve this problem, or how to amend the function or condition of Webstyle.