Is the site down for anyone else? I'm in Cambodia, and gambling is perfectly legal here, so I can't see why it would be blocked. Oddly though, Strike Sapphire loads the same blocked region message I would get when I was in the US, so that has me thinking this could be related if the site is up for everyone else.
Edit: Just used a proxy and it loads. Weird. They do censor here, but it is usually political stuff.
There are some cloud based filtering (e.g., opendns, or MyWoT) system which take user submissions without validation. Could be your system has that or somewhere along that line the site got flagged.
Actually I see MyWoT shows an +80 for SatoshiDICE on trustworthiness, ..., which is fantastic, but has a low confidence likely as so few ratings have been given.
Now if SatoshiDICE were to already be making it into the national firewall / censor systems that would be interesting.