I reproduce the same issue as explain in http://issues.liferay.com/browse/LPS-34071 and i can't find a way to resolve it.
With Internet Explorer 9 and Liferay 6.0.6 CE, when an user try to delete a portlet with the "close icon" and when he choose to "Cancel" or click on "Close" in the confirmation box.
The portlet is removed although the user canceled the action.
Do you know a way to resolve this issue ? Does a fix version exist