IE 8 and Firefox won't connect to one website

Hi,
I hope this is the right forum to post this question. I've used Megaupload for several years to share files. Two days ago, it's pages suddenly stopped working on my internet connection. I had changed no settings and downloaded no new programs. However, when I put in the address, the message came back that my browsers (IE 8 Firefox) couldn't display the webpage.

I tried hooking my laptop up to my modem directly, rather than use my wireless router, and it worked. However, I would like to fix things so I can use my wireless connection again and I'd like to know why it happened.

Thanks!