I am unable to display a file download dialog (IE7) on a screen that includes a scrollableDataTable. However, the same dialog displays just fine on a screen that does not have a scrollableDataTable. I remember reading about a problem with the scrollableDataTable and the z-index property that impacted dropdown menus. Could this be related to that problem? I am using the 3.3.2 SR-1 release.
Solved it. The problem had nothing to do with the scrollableDataTable or z-index after all. I was using an h:commandLink on the page that worked and an a4j:commandLink on the one that wasn't.