Meaning of the line marker with 'blue ball' when stepping through code in VS2008? [duplicate]

This question already has an answer here: What does a blue dot beneath the Visual Studio breakpoint mean? (1 answer) 开发者_开发百科 Closed 4 years ago.

Can anyone tell me what this icon (with the blue ball) means, as opposed to the normal step-through marker without the ball?

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Do you have any other software installed (code helpers, etc)? I have not seen the blue ball, but there could be a debugging plug-in or other tool that adds the blue balls. I know it is not an advanced breakpoint (see: http://geekswithblogs.net/sdorman/archive/2009/02/14/visual-studio-2008-debugging-tricks-ndash-advanced-breakpoints.aspx)