When 2 (or more) users keep voting mostly for each other with no apparent reason (ie, I spend all my votes on a active day here in the site, but they are given to random users) the system has a bad tendency to start blowing bells and whistles around those accounts.
If I go right now and start up voting the questions of another specific user (no matter who he/she/it is) probably by tomorrow all those votes will be marked down and reversed by the system.
Note that Ask Ubuntu is part of the Stack Exchange network and this happens globally around all sites that belong to it, it is not unique or related to any other policies.
The reason the votes where reversed is clear on the moderator message sent to you, but it does not mean you did something bad or that your contributions are not welcomed. They were reversed simply because they are given by or given to a specific user. That is not accepted behavior in the Stack Exchange network of sites.
It has happened to me that I got a reputation boost from a random unknown user, probably I helped in some way and he thought that giving me reputation was the way to go, those were reversed the next day also. Its just how it goes.
There is a threshold were the system deliberately decides that there is a difference between I tend to vote for this user and I vote anything this users posts. Its nothing personal, just how the site works.
Moderators (not only Ask Ubuntu moderators) have powerful tools that allow us to control these situations and make a decision based on that, this was not the first time your accounts and other 2 were discussed and and even though the sheer amount of contribution you guys already gave is enormous, we with the Stack Exchange community decided to act.
Note that only up voting between certain accounts was reversed, all the rest and all your contributions are still there and hopefully we will still see more of good work arriving from those users.
My 5 cents on this story?
Don't take it so serious, your contributions, edits, comments are all noted by the people around you, its not the reputation number you see in your profile that will make you more or less welcomed here on the site. We are all eager to help and to participate, if that is your objective then keep on the good work. That number means nothing at all, actions are worth gold around here.