The popup is actually meant to be the auto update notification (check your avastUI > Settings > Update and you will see that an auto update has just taken place. It appears that these tips/ad popups are piggybacked onto the auto update notification popup and this looks like it messes up the display and sound for the auto update notifications.
If you browse the forums you will see several topics relating to a known bug about updates.
no auto update notification popup (commonly displays an avast! tip - FB Privacy, instead).
no audio voice over for the auto update.
the popup delay timings don’t appear to work either.
These tips popups have in the past been piggybacked with the auto update update notification, so the only way to get rid of them would be to disable the auto update notification, which if you want the update notification (when it works correctly) would remove everything.
Interestingly my win7 netbook gave the correct update popup, voice over and the duration I had set previously also worked, only time will see if this is permanent or a one off (as I had a couple of days ago). Unfortunately that isn’t the case on my XP Pro system, still as before.