Do you get this error in your ULS-log when visiting a page with a DataViewWebPart that’s been changed via SPD?
Error while executing web part: System.NullReferenceException: Object reference not set to an instance of an object.
Try and uninstall the Update: KB2844286 (Security Update for Microsoft .NET Framewok 3.5.1 on Windows 7 and Windows Server 2008 R2 SP1 for x64-based Systems), which was published 09-07-2013. After removing the update, restart your SharePoint server and everything should be back to normal. Remember to hide the update once it’s uninstalled.
I found the solution over at MSDN thanks to Sergio Orru.
[Update July 6, 2013]:
Looks like Microsoft made a hotfix, to fix KB2844286. It’s KB2872441. Acording to Aaron, that Hotfix will break your workflows though, so beware.
And Don’t Try to install the hotfix they offered for it, it broke all our workflows with a “Failed to Start” Error. Ouch!
Hi Aaron
Thanks for the heads up.