Users of IMF 5.1.006 with the Geocortex External Map Visualization Tool enabled will have to upgrade to a newer version of the IMF, as the Virtual Earth API used has reached its end of life (as of September 22, 2008).
I can’t find an online version of the end of life notice, as it appears to have been only emailed to subscribers of the Virtual Earth service. There are forum posts, though:
http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=2942688&SiteID=1
And a blog post:
http://blogs.msdn.com/virtualearth/archive/2008/08/27/virtual-earth-6-0-auto-upgrade-postponed.aspx
