Created Issue: Ajax config feature - Failed to apply a web.config modification to file 'configuration/system.web/pages [12680]

The ajax config feature sometimes throws up exception "Failed to apply a web.config modification to file 'configuration/system.web/pages" and the fix http://features.codeplex.com/WorkItem/View.aspx?WorkItemId=8353 didn't work for me.

Though the feature fails to activate, it still creates all the config entries. Any fix for this?