Please help!!!

I have a popup panel and inside it a form which opens new window when submitted.

When the same form is not inside the popup panel, a new window opens fine.

When it is inside the popup panel on some computers Internet Explorer displays popup warning message (in the top of the web-browser window) asking the user if he/she wishes to allow the popup.

But this is not a popup, this is just new window - how to avoid this?

Here is my code:

<script type="text/javascript">
function func()
{
var form = document.forms.my_form;
window.open ('about:blank', 'Popup_Window', 'resizable=1,scrollbars=1');
form.target = 'Popup_Window';
form.submit ();
}
</script>

<div id="PopupPanel" style="display:none">
<div class="PopupPanel">
<form action="action.php" ...>
</form>
<button type="button" onclick="func()">OK</button>
</div>
</div>

On some computers Internet Explorer does not display any popup warning and opens new window with action.php (while popup blocker is set), on other computers the window is not opened and warning displayed.