Pop-up Window was moved but its image still left behind

I'm using VS 2005 and .NET framework 2.0 SP2 to build an application with a datagridview in it. I'm using Microsoft Word 11.0 Object Library to do the spelling ch开发者_StackOverflow社区ecker on one of the field in datagridview. When it detected a spelling and grammar window would pop-up open on top of the datagridview.

The problem I got was when I moved the pop-up window to the new location, there's still an image of the pop-up window left behind the previous location. The more I moved the more of those copied image would be created on screen.

How I can overcome this problem?

Thanks in advance, Andrew

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This happens when your form stops painting itself.
You're probably making a blocking call to Word's spell-check, which prevents the form from receiving Windows messages and repainting.

To fix it, you'll need to call the Word function from a background thread.