Attaching screen shot of drop down as rendered with a single portlet on the page. The location of the drop down will depend on where on the page the portlet is located and how many other portlets there are on the page. In certain cases it will get rendered off the bottom, right of the viewing area completely.

Note that this only seems to happen with Liferay 6. With Liferay 5, the drop down renders in a correct location relative to the input text box so the problem is likely a conflict with the Liferay 6 theming.

One last note. Attaching a screen shot that shows that the top: style of the div that renders the drop down list is calculated to be 408 pixels. As the screen shot shows, turning this off using Firebug puts the div in the correct position.

The calculation for this "top" value is likely being done from a location that is relative to one of the containment elements rather then the window.