System.InvalidProgramException was unhandled by user code
  Message="Common Language Runtime detected an invalid program."
  Source="SolpartWebControls"
  StackTrace:
       at Solpart.WebControls.SPDataMappings..ctor()
       at Solpart.WebControls.SolpartMenu..ctor()
       at DotNetNuke.NavigationControl.SolpartMenuNavigationProvider.Initialize()
       at DotNetNuke.UI.Skins.NavObjectBase.InitializeNavControl(Control objParent, String strDefaultProvider)
       at DotNetNuke.UI.Skins.Controls.SolPartMenu.OnInit(EventArgs e) in E:\EroCityDev\admin\Skins\SolPartMenu.ascx.vb:line 974
       at System.Web.UI.Control.InitRecursive(Control namingContainer)
       at System.Web.UI.Control.InitRecursive(Control namingContainer)
       at System.Web.UI.Control.AddedControl(Control control, Int32 index)
       at System.Web.UI.ControlCollection.Add(Control child)
       at DotNetNuke.Framework.DefaultPage.Page_Init(Object sender, EventArgs e) in E:\EroCityDev\Default.aspx.vb:line 465
       at System.Web.UI.Control.OnInit(EventArgs e)
       at System.Web.UI.Page.OnInit(EventArgs e)
       at DotNetNuke.Framework.PageBase.OnInit(EventArgs e)
       at System.Web.UI.Control.InitRecursive(Control namingContainer)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

Visual Studio breaks on Line 974:

InitializeNavControl(Me, "SolpartMenuNavigationProvider")

The site I got the error on was a 4.3.4 starterkit under visual studio, with 1 custom module that needed a small tweak. I tought It was a Visual studio quirk, but rebooting didn't help. I will try to just install a new starterkit instance to do my work.