Using a simple portlet to create draggable and/or modal popups in Liferay seems to work in all the major browsers. However, with Liferay and IE7, I can see a z-ordering issue under very specific circumstances.

1) In Liferay, run a portlet that creates a popup (draggable or modal - either on shows the issue).
2) Use IE to view the portal page and create a popup WITHOUT logging in.

This should work fine,

3) Login to Liferay using a valid account (test@liferay.com, test is fine)
4) Again view the portal page and create a popup.

Once you login, the portal page with the Noir theme (which is new with Liferay 4.3.3) creates a footer that is actually a portlet. The footer portlet obscures portions of a modal popup or any draggable popup that you move over it. This appears to be a z-order issue with IE7 and Liferay. The same issue does not appear when using Firefox or Safari. I'll attach some screen shots to help illustrate.