It looks like this customer communication thing is catching on. After three consective problem Sundays, Microsoft decided it might be a good idea to tell its network customers what was happening (no more nebuleous statements blaming the "Internet").

From Microsoft's web page:

December 5 Connection Problems As you may know, at 7 P.M. on the night of Sunday, December 5, there were severe connection problems, which resulted in disconnections and lag. This was because a reconfiguration in our datacenter was made at that time. Due to a communication breakdown (which we are assuring will not happen again), word of this change did not reach those of us who inform the players of such a reconfiguration. Had we known about the reconfiguration, we would have warned you not to play while it was going on.

Adding to the problem, after the reconfiguration stopped, we gave the players the "all clear" to re-enter the game. Unfortunately, within 20 minutes, there was a datacenter problem, and this caused more connection disruptions. We are still investigating the cause of this problem; it was not caused by another reconfiguration but probably was a consequence of the previous one.

We deeply apologize for these problems, both that a reconfiguration was made during a busy time, and that you did not get adequate warning.

NOTICE: Datacenter Reconfiguration December 6

In an effort to eliminate further connection disruptions in our datacenter, a reconfiguration is being done late on December 6. This will begin at midnight and end at 5 A.M., Pacific time. It is strongly advised that you do not play AC during this time, as bad lag can hit at any moment. After 5 A.M., cautious play is advised until we are sure the new configuration is stable.