Due to some vagaries in the system, we have some users who "belong" to multiple teams.
I think I've corrected the problem so it won't crop up again.
A couple of players' team memberships were manually reduced to 1. If it was you, and you're suddenly on the wrong team, post in the forum and I'll fix it for you.
For everyone else, when you go to the event list you may be redirected to a "You're on multiple teams" page, and asked to click the team you wish to remain on. Your "join date" will not change, so you'll still be able to participate in the events. You'll simply be de-listed from the other teams.
As always, post in the forums if you need help.