Assassin's Creed: Brotherhood have been interrupted. That's not due to the current national holiday; rather, it's because some players seem to be having trouble downloading the game's latest title update, locking them out of any and all of Brotherhood's online offerings.
Ubisoft has acknowledged the error, and is currently working to repair the damage. We'll let you know when you can get back to your regularly scheduled murder and stuff.
Update: Whatever was causing the update hiccup has been remedied, according to Ubisoft. We just downloaded the patch with no problem, and would wager that you can now do the same.