Gus, there's a thread about this a few threads down.
I had the same problem a while back. A computer savvy acquaintance uninstalled the new java and replaced it with Java Legacy in less than 15 minutes and I haven't had any problem since.
Since your mac is under warranty, apple support may be able to guide you through this.
If not, look again at the link and see if there isn't a Mac option somewhere lower down on the page, or do a search for one.
If all else fails, there are game experts who will do a "screen share" online and fix it in a matter of minutes. There's a fee, but it's probably reasonable.