lolshield: Text does not work

Hi all,

I just gambled with my new lolshield. The usual demos ran fine; then I wanted to display some text, but the shield remained dark. So I stripped down the code to display only one letter:

#include "Charliplexing.h"
#include "Font.h"
#include "Arduino.h"

void setup ()
{
    LedSign::Init ();
}

void loop ()
{
    LedSign::Clear ();
    delay (500);
    LedSign::Set (4, 4, true);
    delay (500);
    Font::Draw ('A', 0, 0); 
    delay (500);
}

I expected that the letter 'A' blinks, but again the shield remained dark. If I delete the Font::Draw command, then the LED at (4,4) blinks as expected.

What am I missing here? (BTW: I'm using the IDE 1.0.1)

best regards
Andreas