Update on the 501 / AJAX error

I originally thought that the Microsoft bug was just for IE 7 & IE 8 on Windows XP.  We had fixed the problem in XP with IE 7.  But we had people upgrading to Windows 7 with IE 8 and they started getting the problem again. That XP only info was tied to something read from a blog post. With more careful reading of the actual MS article, it looks like this bug applies to all users of IE 7 & IE 8, no matter what version of Windows you are using.  The linked Microsoft KB article has instructions for how to apply the fix to your registry.