Dotnetnuke Actions button missing from site

I am using DNN 5.1 on a project and something's happened that I cannot quite figure out. The control button which controls the actions of any html module has gone missing. If I check the event viewer of DNN, this is what I get:

Message: DotNetNuke.Services.Exceptions.ModuleLoadException: Object reference not set 
to an instance of an object. ---> System.NullReferenceException: Object reference not    
set to an instance of an object. at otNetNuke.UI.Containers.ActionBase.get_ActionRoot() 
at DotNetNuke.UI.WebControls.SolPartActions.BindMenu() at 
DotNetNuke开发者_JS百科.UI.WebControls.SolPartActions.Page_PreRender(Object sender, EventArgs e) --- 
End of inner exception stack trace

It seems to be a problem with the Skin file because if I switch to another skin ,the Actions button is back as normal. What I am not getting though is how this has changed since the last time I successfully used it.

If someone has some suggestions I would appreciate it.

I would suggest looking into your module container .ascx file and remove the references to solpart! and replace with a different provider. I find the standard ones are very slow. I will grab the code from one of my container .ascx files for you to examine - this uses another menu provider to handle the little admin menu's

<%@ Control Language="vb" Codebehind="~/admin/Containers/container.vb" AutoEventWireup="false"
    Explicit="True" Inherits="DotNetNuke.UI.Containers.Container" %>
<%@ Register TagPrefix="ddr" TagName="ACTIONS" src="~/DesktopModules/DDRMenu/Actions.ascx" %>
<%@ Register TagPrefix="dnn" TagName="TITLE" Src="~/Admin/Containers/Title.ascx" %>
<%Dim ModuleTitle As String = DotNetNuke.UI.Containers.Container.GetPortalModuleBase(dnnTITLE).ModuleConfiguration.ModuleTitle()%>
<dnn:title runat="server" id="dnnTitle" visible="false" />                
<h3><%= ModuleTitle %></h3>
<div class="tab_edging" id="ContentPane" runat="server" style="border:1px solid white">
</div>      
<div class="spacer">
<ddr:ACTIONS runat="server" />
</div>

we have installed an extra menu provider from http://www.dnngarden.com/Download.T87.aspx which i suggest you take a look at!

The problem is probably the container or some errant javascript. I would try switching to a different default container first. If that doesn't do it, look to see if there is any Javascript that is throwing errors (I generally do this in the Firefox Error console, but there are many ways).