I'm trying to have two view controls on my module, but I can't seem to be able to call the second one from the first one, it just goes to an empty page.

In my .dnn file I set the 2 controls as follows:

            <control>
              <src>DesktopModules/NewsML/ViewNewsML.ascx</src>
              <type>View</type>
              <helpurl></helpurl>
            </control>
            <control>
              <key>ViewDetails</key>
              <title>View Details</title>
              <src>DesktopModules/NewsML/ViewNewsDetailML.ascx</src>
              <type>View</type>
              <helpurl></helpurl>
            </control>

And to call it from the first control I'm using:

<asp:HyperLink ID="HyperLink2" NavigateUrl='<%# NavigateURL(portalSettings.ActiveTab.TabID,"ViewDetails","itemID=" & DataBinder.Eval(Container.DataItem,"ItemID")) %>' runat="server">Details</asp:HyperLink>

What am I doing wrong?

That's by design for a control loaded by DNN(Edit or View) that is not the default control. If you want to keep the skin, you'll need to load the control dynamically from within your module.

Thanks.