a4j:commandButton not working in second clic

Hello ! I have a problem that i can't recognize the cause, this is my code :

<a4j:commandButton id="afficheBtn"
    style="background: url('images/btn_affich.gif');height: 19px; width : 68px;"
    render=":lcebgch :restitutions" >
    <a4j:ajax event="click" execute="@this"
        onbegin="javascript:lanceRestit();"
        oncomplete="javascript:parent.AffichFileList(stat, changeTypeRestit(), oneChecked1());"></a4j:ajax>
</a4j:commandButton>

it's working fine in the first click, but nothing happens in the other clics !!

Please, do you have any idea what could be the problem !