A very simple innocent code is not working in IE, though it's working properly in FF.

Code:
<a href="#" class="menu" onclick="window.open('mypage.php?id1=99&id2=69','_blank','scrollbars,height=330,width=460'); return false;">My content</a>
When I click on the link for the first time, it works for both. However, if I click on the link again without closing the first one, in IE, I get error. In FF, windows open n times without any problem.

Know why it's happening? Thanks.