You may have already solved this problem by now, but in case it's of any use you may be interested in this article. According to the Washington Post there has been an extension on Megaupload files which stll has a day or two left to run as I type this, so you may still be in time.

You may also get some help if you visit the Megaretrieval site, where legal users of Megaupload are being offered help and advice. Obviously you are not alone, and everyone including the governement accepts that plenty of users were storing legitimate date which they need to access, so there are people out there trying to solve this problem. As well as the above links you could try contacting the Electronic Frontier Foundation, a not for profit organization who are also trying to help with this.

Hope this helps and that you get your files back.