Nobody really knows what it is, or why it's announcing that. As I mentioned, even a few Blizzard employees have no idea what it is, though they're looking into it. The only 'ice stone' that crops up when Googling or Wowwiki'ing around to find this thing is the objects from the Midsummer Festival that we interacted with last year. It's possible that the team responsible for world events was working on an update to the Midsummer Fire Festival and crossed some wires somewhere. After all, if any of the holidays need an urgent update, it would be that one.
Midsummer is one of the few holidays with an active, ongoing story. It's not just fireworks and presents, but there are sinister things happening! Remember, this past year it was the Twilight's Hammer trying to summon Ahune into our world (via Outland), and there was some Naga drama thrown into the mix. Maybe the storyline has moved on since last year? The Twilight's Hammer is all up on Yogg-Saron's junk now, as we see in Ahn'Kahet. Maybe they're going to try a new summoning, this time in Northrend? Maybe it's a world event sort of thing this time around, and that's why the Ice Stone melting is a server-wide announcement.
Or it's just a mundane bug and doesn't really mean anything at all.
Update: Yes, they are looking into it.
Love is in the Air and on WoW Insider. Check out our continuing coverage of the event and our guide to earning the achievement. And you better hurry; the holiday only lasts five days!