Error 14447 in run-time session

Any suggestion on what causes this, run-time only, error  the code works at development time.

The rcode is up to date , run-time and development using the same assemblies,

OE 11.6.3

Could not find class or interface System.IDisposable. (12886)
TYPE-OF 'System.IDisposable' not allowed. TYPE-OF target must be a user defined type. (14447)
** src/be/cce/ccetools/base/ObjectHelper.cls Could not understand line 54. (198)

I'm also very confused how I can get something that looks like a compile error when I'm running a session with -rr

[mention:04fbfb2e92784123a464ff2aade602b1:e9ed411860ed4f2ba0265705b8793d05]|| , [mention:6e3b17cb0ff148039a2aabb4c7834ce4:e9ed411860ed4f2ba0265705b8793d05] suggested asking this to you on the community

 /*------------------------------------------------------------------------
    File        : ObjectHelper
    Purpose     :
    Syntax      :
    Description :
    Author(s)   : cvb
    Created     : Fri Aug 26 11:51:47 CEST 2011
    Notes       :
  ----------------------------------------------------------------------*/

using Progress.Lang.*.

routine-level on error undo, throw.

class be.cce.ccetools.base.ObjectHelper:

    constructor static ObjectHelper():
    end constructor.

    /*------------------------------------------------------------------------------
            Purpose:
            Notes:
    ------------------------------------------------------------------------------*/
    method public static Progress.Lang.Object GetFirst(input iTypeName as character):

        return getNext(?,iTypeName).

    end method.

    /*------------------------------------------------------------------------------
            Purpose:
            Notes:
    ------------------------------------------------------------------------------*/
    method public static progress.lang.object GetNext(input iStartFrom as progress.lang.object, input iTypeName as character  ):

        def var oObject as Progress.Lang.Object.

        if valid-object(iStartFrom)
        then iStartFrom:Next-Sibling.
        else oObject = session:first-object.
        OBJECTLOOP:
        do while valid-object(oObject):
            if oObject:GetClass():TypeName = iTypeName then leave OBJECTLOOP.
            oObject = oObject:Next-Sibling.
        end.

        return oObject.
    end method.

    method public static void DeleteObject(input iObject as progress.lang.object  ):
        if valid-object(iObject)
        then do:
            if type-of(iObject,System.IDisposable)
            then cast(iObject,System.IDisposable):Dispose().
            if valid-object(iObject)
            then delete object iObject.
        end.

    end method.
end class.

after