After adding a 'List Container' to a new page, I click on the configure (gear) icon to configure it... I get the following:

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: 
An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace: 
[NullReferenceException: Object reference not set to an instance of an object.]
   MonoSoftware.MonoX.ListEditorPart..ctor() +149
   lambda_method(Closure , Object[] ) +42
   MonoSoftware.Core.ActivatorExtension.CreateInstance(Type type, Object[] args) +422
   MonoSoftware.MonoX.PropertyGridEditorPart.#Fs(WebEditorAttribute editControlAttribute, PropertyDescriptor property) +108
   MonoSoftware.MonoX.PropertyGridEditorPart.#Ds(PropertyDescriptor property) +112
   MonoSoftware.MonoX.PropertyGridEditorPart.CreateChildControls() +155
   System.Web.UI.Control.EnsureChildControls() +103
   MonoSoftware.MonoX.PropertyGridEditorPart.SyncChanges() +62
   System.Web.UI.WebControls.WebParts.EditorZoneBase.OnSelectedWebPartChanged(Object sender, WebPartEventArgs e) +162
   System.Web.UI.WebControls.WebParts.WebPartEventHandler.Invoke(Object sender, WebPartEventArgs e) +0
   System.Web.UI.WebControls.WebParts.WebPartManager.OnSelectedWebPartChanged(WebPartEventArgs e) +91
   System.Web.UI.WebControls.WebParts.WebPartManager.BeginWebPartEditing(WebPart webPart) +303
   MonoSoftware.MonoX.BasePart.#vj(Object sender, WebPartEventArgs e) +64
   System.Web.UI.WebControls.WebParts.WebPartZoneBase.RaisePostBackEvent(String eventArgument) +1351
   MonoSoftware.MonoX.PortalWebPartZone.RaisePostBackEvent(String eventArgument) +305
   System.Web.UI.WebControls.WebParts.WebPartZoneBase.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +169
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3259