User not prompted for client certificate pass phrase

[Florent Parent <Florent.Parent@xxxxxxxxxx>]

When I use w3m (outside emacs) to my https server, w3m prompts me for my 
client certificate pass phrase ("Enter PEM pass phrase:").

Using the same URL in emacs-w3m, I receive no prompt for the pass phrase 
and the page never appears (w3m process in background hangs)

  PID TT  STAT       TIME COMMAND
19708 pc  Ss+     0:00.02 /usr/pkg/bin/w3m -no-cookie -o 
follow_redirection=0 -o user_agent=Emacs-w3m/1.3.3  -dump_extra 
https://myserver...

Any idea what is wrong?

emacs-w3m 1.3.3
w3m 0.4
emacs 21.2.1

Thanks
Florent