Thanks to Gottwald for letting me know that a bug report has been filed for this issue and it's been addressed as we speak.
Last week, I blogged about the warning if closing multiple tabs not working.
Infact, the team have known that this was a major issue well before they released the Version 3 last week. To be more exact, the problem was report first in February.
https://bugzilla.mozilla.org/show_bug.cgi?id=419009
