window.open IE 8 show download dialog

[Arkhron]

Hello everyone
I have a form in a web page like this

<form name=morosos onsubmit="abrirCuatro(); return false;" method=GET action="[URL unfurl="true"]http://jupiter.contaduria.gov.co/bdme/"[/URL] target="_blank">
  <label class=SubtitularAzul>Boletín De Morosos Del Estado</label> <br>
<label class=menuproductos>Nit a Buscar:</label><br>
<input name=num type=text>
<input type=submit class=formulario value="Ver Moroso">
</form>

The function abrirCuatro() is defined like this:

function abrirCuatro() {

var nit = document.morosos.num.value;

window.open("[URL unfurl="true"]http://jupiter.contaduria.gov.co/bdme/?MIval=/Tresultado_consulta_morosos2.htm&cod=1&num="[/URL] + nit );
window.open("[URL unfurl="true"]http://jupiter.contaduria.gov.co/bdme/?MIval=/Tresultado_consulta_morosos2.htm&cod=1&num="[/URL] + nit.substring(0, nit.length - 1));
window.open("[URL unfurl="true"]http://jupiter.contaduria.gov.co/bdme/?MIval=/Tresultado_consulta_morosos2.htm&cod=2&num="[/URL] + nit );
window.open("[URL unfurl="true"]http://jupiter.contaduria.gov.co/bdme/?MIval=/Tresultado_consulta_morosos2.htm&cod=2&num="[/URL] + nit.substring(0, nit.length - 1))

}

Too simple.

Problem is when the function try open all the 4 pages. Sometimes works fine, opening the pages OK in different IE windows; but sometimes, for example, the function open page 1 and 2 OK, page 3 do not open but just show the download dialog box and ask me for save the file (without extension) some place on my pc, then open OK page 4. This is a random behavior. Other times open just one page OK and the other 3 show the download dialog. Every time changes the page which ask to download and save.

This is an IE8 bug? or i'm invoking in the wrong way the function? or bad definition of the form ? or maybe there's a missing parameter I'm not filling?

Thanks for your replies
(sorry about my english)





LEY DE EDWARDS SOBRE EL ESFUERZO/TIEMPO.
Esfuerzo x Tiempo = Constante.
Dado un tiempo inicial grande para hacer algo, el esfuerzo inicial será pequeño.
A medida que el tiempo se aproxima a cero, el esfuerzo tiende a infinito.

-"Murphy fue un optimista"-