Hello!

I have an urgent problem.

I upgraded a site from 4.5.2 to 4.7.1 last week.
It is working fine on my local machine, but our client has just called to say that all second level nodes in the content tree in the back end won't expand on the live site.
I have checked the log and I have lots of these errors:

At /umbraco/webservices/TreeDataService.ashx?rnd=692296c312fe46aebf474f8943da9671&id=-20&treeType=contentRecycleBin&contextMenu=true&isDialog=false&rnd2=84.6 (Referred by: http://www.dga.eu.com/umbraco/umbraco.aspx): 

Running it with Chrome Firebug I get the actual error as:

[NullReferenceException]: Object reference not set to an instance of an object.
   at umbraco.cms.presentation.Trees.BaseContentTree.GetUserActionsForNode(Document dd)
   at umbraco.cms.presentation.Trees.BaseContentTree.Render(XmlTree& Tree)
   at umbraco.loadContent.Render(XmlTree& tree)
   at umbraco.presentation.webservices.TreeDataService.GetXmlTree()
   at umbraco.presentation.webservices.TreeDataService.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

I have checked the permissions on the site and they seem ok, I tried restarting the app pool but made no difference.

What would be causing this?

Bex