Problem with System.Windows.Forms.WebBrowser

I used a lot System.Windows.Forms.WebBrowser in my LSSaver project to process the pages. Recently I got a feed back that LSSaver stops to load the blog titles and is blocked there. The problem seems to happen on a WinXp + IE6 platform.

After investigation, the problem comes from a null pointer exception, but why there is a null pointer? A step by step debug showed me that when using WebBrowser’s DOM to retrieve certain HTML element, the HtmlElement.NextSibling returns an invalid pointer even when there is no more sibling of the calling HtmlElement object. It seems that this is a known issue in the .NET framework:
http://connect.microsoft.com/VisualStudio/feedback/details/304466/htmlelement-nextsibling-returns-incorrect-value

Anyway, I won’t rely on the NextSibling is null or not, I get the number of children from the parent, then rely on this count when traversing all the children elements. The problem is fixed.