Jquery dialog box disappering after some time

Question

I have use jquery dialog box in which I have populated drop down lists using ajax,it is working fine on I.E 6 but on mozilla when I click the button to show the dialog box for the desired purpose.After approx 5 sec later it disappears. My code is something like

var confirmDialog = null;
function processConfirm() {
     $(confirmDialog).dialog("close");
    }

function showDialog()
{
    document.forms[0].displayDownload.value='true';
    $('#dialogbox').removeClass("hidden");
    confirmDialog=$('#dialogbox').dialog({
          bgiframe: true,
          modal: true,
          height: 200,
          width: 350,
          resizable:false
    });      
}

With html:

<div id="dialogbox" title="${PAGE_TRANSLATION_KEYS['DOWNLOAD_PROD_DATA']}" class="hidden">
  <table align="center"> 
    <tr><td> </td><td></td></tr> 
    <tr> <td></td> </tr> 
    <tr><td> </td></tr> 
    <tr >
    <td width=20% colspan="3" align="right">${PAGE_TRANSLATION_KEYS['SBU']}:</td>
    <td width=80% colspan="5"> 
    <html-el:select name="maintenanceSimulationForm" property="sbuOID" styleId="sbuOID" onchange="submitAjaxForSBU('getAuthorizedForecastUnits',forecastUnit_callback)">
    <html-el:option value=" ">-${PAGE_TRANSLATION_KEYS[SLCT]}-</html-el:option> <c:forEach items = "${form.sbuOptions}" var = "sbuOptions"> 
    <html-el:option value="${sbuOptions.sbuOID}"> (${sbuOptions.sbuID}) ${sbuOptions.sbuName} </html-el:option>  </c:forEach>  </html-el:select></td></tr>
    <tr><td width=20% colspan="3" align="right">${PAGE_TRANSLATION_KEYS['FORECAST_UNIT']}: </td><td width="80%" colspan="5">
    <html-el:select name="maintenanceSimulationForm" property="forecastUnitOID" styleId="forecastUnitOID" onchange="submitAjaxForForecastUnit('getAuthorizedFactoriesForSBU',factory_callback)"> 
    <html-el:option value="">-${PAGE_TRANSLATION_KEYS[ALL]}-</html-el:option>
    </html-el:select></td></tr> 
    <tr> <td width="20%" colspan="3" align="right">${PAGE_TRANSLATION_KEYS['FACTORY']}:</td> <td width="80%" colspan="5">
    <html-el:select name="maintenanceSimulationForm" property="factoryOID" styleId="factoryOID" onchange="submitAjaxForFactory('getAuthorizedProductLinesForFactory',productLine_callback)"> 
    <html-el:option value="">-${PAGE_TRANSLATION_KEYS[ALL]}-</html-el:option> </html-el:select></td> </tr> 
    <tr> <td width="20%" colspan="3" align="right">${PAGE_TRANSLATION_KEYS['PRODLINE']}:</td> <td width="80%" colspan="5">
    <html-el:select name="maintenanceSimulationForm" property="productLineForecastUnitAsscnOID" styleId="productLineForecastUnitAsscnOID"> 
    <html-el:option value="">-${PAGE_TRANSLATION_KEYS[ALL]}-</html-el:option> </html-el:select></td> </tr> 
  </table> 
  <ul class="commandButtons">
    <li><button onClick="getDownload()">${PAGE_TRANSLATION_KEYS['DOWNLOAD']}</button></li> 
    <li><button onClick="processConfirm()">${PAGE_TRANSLATION_KEYS['CANC']}</button></li>  
  </ul> 
</div>

How can I fix this?