IE 7 popup refresh problem

Anyone have encountered the problem where my modal popup window requires refresh when submit to the server and upon returning, IE7 opens up another windows. It didn't happen in IE6.

I used the common script to create a modal popup window:

modalWin = window.open(String(sURL), "", sWinFeat);

Over at my jsp:

function refresh() {
// Fix: to avoid double submission during check
$('button').disabled = true;
waitDialog();

document.forms[0].action = '/myAction/refresh.do';
document.forms[0].submit();
}

Did IE7 behave this way now or is my script in jsp above is wrong?

Thanks