This week I wrote new blog post on our team blog webtopics which talks about above error and reason for it ..

You can visit here : http://blogs.msdn.com/webtopics/archive/2009/06/19/intermittently-system-web-httpexceptions-a-field-or-property-with-the-name-columnname-was-not-found-on-the-selected-data-source-is-thrown-when-the-application-is-under-heavy-load.aspx 

 

Till then bye bye :)