After deselecting some of the tabs under "Tab options" and there are only a few left, say 4, the scrolling is still enabled, even though it is not necessary. You're able to scroll all the tabs off the screen. After a restart the arrows for scrolling is gone and everything is correct.
Similarly, if there are only a few tabs visible and you choose all to be visible, scrolling is not enabled straight away (the arrows don't show), a restart is again necessary.
(Of course, this is only really a problem if you have the large images enabled or your screen resolution is very low.)
