When operating in a right-to-left environment (direction: rtl), the selected tab (.ui-tabs-selected a) does not display correctly with "position: absolute" in place. This is consistent across IE7, Firefox, and Safari.
Specifically, the A tag displays, but the child SPAN tag does not; it seems to be somewhere else (unseen) on the page. This renders just the right stub of the tab image, but not the full image nor the text.
Removing "position: absolute" from the ".ui-tabs-selected a" selector seems to fix the problem. The only downside is that both "top" and "z-index" also become inoperable, and the selected tab now displays 1px higher, which also reveals the panel top boundary line.
Unselected tabs do not display this problem.
I am using jQuery UI 1.5b4 with the standard ui.tabs.css and ui.tabs.js.