'Class not registered' error appears when running an Explain Plan (4235804)

When running the Explain Plan in Toad, the following error appears:

'System.Runtime.InteropServices.COMException
Class not registered (exception from HRESULT: 0x80040154 (REGDB_E_CLASSNOTREG))
Stack trace:
    at System.Windows.Forms.UnsafeNativeMethods.CoCreateInstance (Guid & clsid, Object punkOuter, Int32 context, Guid & iid)
    at System.Windows.Forms.AxHost.CreateWithLicense (String license, Guid clsid)
    at System.Windows.Forms.AxHost.CreateInstanceCore (Guid clsid)
    at System.Windows.Forms.AxHost.CreateInstance ()
    at System.Windows.Forms.AxHost.GetOcxCreate ()
    at System.Windows.Forms.AxHost.TransitionUpTo (Int32 state)
    at System.Windows.Forms.AxHost.CreateHandle ()
    at System.Windows.Forms.Control.CreateControl (Boolean fIgnoreVisible)
    at System.Windows.Forms.Control.CreateControl ()
    at System.Windows.Forms.Control.ControlCollection.Add (Control value)
    at Quest.Toad.ExplainPlan.ExplainPlanControl.FillExplainViewer (Boolean bDoNotAskConnectionData)'