Oooh I had one of these once - a bug in the forwarding engine of a J-box
caused all through traffic to drop whilst maintaining adjacencies and
VRRP mastership. It took two incidents to determine what the cause of
the fault was.
So much for redundancy...
Fortunately it was at the tail end of a maintenance window.
Unfortunately
it affected a similar size user base to the Telia fault (but luckily it
seems no-one noticed enough to publicise it 
BB