Edit (6/2/2012): Right. I should've remembered to do this as soon as possible. To participate in the event, go here and log in with your username. After that, scroll down until you find a button after the score card. Click it, and you'll be put in for that day. Do this daily, and you'll get good rewards! ...Unfortunately, I realize now that it's too late to get the top-most prize, but since I doubt anyone else is actually planning on participating, I guess I'm safe.
I thought about putting this in the wiki news section, but then realized it may not exactly fit due to it not being news about the wiki. Rather, it's news about the game itself, that all current players must read!
In addition to releasing the next version of the game, 5.00, BigBugStudios has also released an update to the game launcher that checks out whether or not you're running the latest version, current events, etc. You'll probably want to get it, and it may be necessary to update to 5.00.
The download link for it is here . Simply unzip the folder's contents into the root folder you installed 12 Tails Online in, and overwrite all the files. After that, just run the launcher like you always do and it should work just fine.
Also of note is what I believe is a new event, the "Check In" event. For every day of June, you'll log into your account on a special page on the 12 Tails site, and you'll get a stamp for that day you've checked in. Get enough stamps, and you'll get rewards. These range from General Boxes, to Golden Lotto Tickets, so you'll definitely want to participate! I'll edit this blog post later once I've got the event confirmed to work and how to do it yourself.
That's all for now! I'll keep working on mission pages each day, so keep an eye on those as well!