Così funziona.. ma magari c'è un sistema migliore...

<html>
<head>
<title>Parent</title>

<SCRIPT LANGUAGE="JavaScript1.2">
var normaldoc;
var normalwin;

function MouseList()
{
if (navigator.appName == 'Netscape' &&
(e.which == 3 || e.which == 2 || e.which == 1))
return false;
else if (navigator.appName == 'Microsoft Internet Explorer' &&
(event.button == 2 || event.button == 3 || event.button == 1)) {
return false;
}
return true;
}

function UnBlockMouse()
{
document.onmousedown=normaldoc;
if (document.layers) window.captureEvents(Event.MOUSEDOWN);
window.onmousedown=normalwin;
}

function BlockMouse()
{
normaldoc = document.onmousedown;
document.onmousedown=MouseList;
if (document.layers) window.captureEvents(Event.MOUSEDOWN);
normalwin = window.onmousedown;
window.onmousedown=MouseList;
setTimeout('UnBlockMouse()',5000);
}

</SCRIPT>

</head>
<body bgcolor="red">
<center>
clicca sotto e disabilita il mouse per 5 secondi

<input type="button" value="disabilita" onclick="BlockMouse()">
</center>
</body>
</html>