tab content not shown properly - bug?

[Savvas]

I've noticed this strange behaviour but I'm not sure how to phrase it
properly.. maybe there's already a bug for this.
Has anyone noticed that when switching between tabs in programs with
tabbed browsing, such as mozilla firefox, it doesn't show the tab
contents properly? When I click to see (or close) a tab, the contents
of the previous tab are shown.
If I mouseover the tab contents, it starts revealing the contents of
the current tab.
In addition, if I switch to another tab and go back, it fixes this
glitch and shows the tab contents properly.

Has anyone noticed a similar problem? Is there a bug report for this?
I use gnome and ubuntu intrepid beta (updated) and nvidia graphics
card and driver if that matters