We have an issue with Templates and Views in Umbraco Backoffice. No reference to when the problem occured. First seen in v7.3.0 and still present in v7.3.3

Whats been tryed: - Full rights on Files and Folders - Upgrade from v7.3.0 to v7.3.3 worked fine - Sites and rest of Backoffice works as expected - Tryed debugging through EditView.Onload. (Is the user always anonymous here?) - Same issue on development, test and production environments

Errors:

Logfile: 2015-12-02 16:29:36,031 [161] http://site.domain.com/umbraco/settings/views/editview.aspx?treetype=templates&templateid=1279 ERROR Umbraco.Core.UmbracoApplicationBase - An unhandled exception occurred System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.NullReferenceException: Object reference not set to an instance of an object. at Umbraco.Web.UI.Umbraco.Settings.Views.EditView.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.HandleError(Exception e) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) at System.Web.UI.Page.ProcessRequest() at System.Web.UI.Page.ProcessRequest(HttpContext context) at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)