I'm receiving an error while trying to edit any content item in the Content Tree,
this is the error message
Can you help how to fix it?
Updated: Trace information
[InvalidOperationException: ContentEditorDataContext] Sitecore.Diagnostics.Assert.IsNotNull(Object value, String message) +55 Sitecore.Shell.Applications.ContentManager.ContentEditorForm.OnLoad(EventArgs e) +184
[TargetInvocationException: Exception has been thrown by the target of an invocation.] System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor) +0
System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments) +76
System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) +211 System.Reflection.MethodBase.Invoke(Object obj, Object[] parameters) +35 Sitecore.Web.UI.Sheer.ClientPage.OnLoad(EventArgs e) +337 System.Web.UI.Control.LoadRecursive() +71
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3178
Update: the issue appears on a load balancing environment where having two Sitecore CMS instances that point to the same databases.