accents in the slide title

Dear all,
I have experienced problems to put accents like \'a, \~a, etc in the slide titles. The 
accents in the body of the slide is working just fine.
A quick look in the ppower4 mailing archives retuned no sufficient explanations for
me to get around this (newbie). Please could anybody possibly help me?
Thanks in advance,
Fred

P.S.:my header goes,

\documentclass[20pt,landscape]{foils}
\usepackage{mdwslides}
\usepackage[english]{babel}

\usepackage{hyperref}
\hypersetup{
  pdfstartpage=1,
  pdfmenubar=true,
  pdftoolbar=true,
  pdfpagemode={None}
}

\usepackage{pause}
\usepackage{graphicx}

it has no difference on using the brazil-babel package.