What version of LV are you using?
This was a bug in earlier versions that was fixed:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/862567530005f09e862567d10077407a?OpenDocument
and also:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/862567530005f09e862567d10077407a?OpenDocument
2006 Ultimate LabVIEW G-eek.