navigatetostringsync problem

[carlos@agpsoftware.com]

Hi,
I'm having a problem with navigatetostringsync method. The same really simple html content works fine with navigatetostring and shows html content correctly. However, navigatetostringsync returns success = false and TxWebErrorStatus = 0

Code:

thisform.oAntView.object.NavigateToStringSync(m.codigo_html, @m.exito, @m.TxWebErrorStatus)

Txt attached is html content of m.codigo_html variable.
m.exito returns .f. (false) and  m.TxWebErrorStatus returns 0

Any idea of what am i doing wrong?
TIA