For starters, just to make sure we are on the same page, the correct URL is
http://www.arcadeshop.com/ and it works fine for me as I am typing this.
Are you trying to access the site from work or home? If from work, your network administrator may have blocked the site.
If you are at home, can you access it through the IP address
http://69.36.163.232/ ? If so, then you are having DNS issues. Also, do all the standard things, i.e. scan for viruses/trojans/spyware...make sure all your scanning programs have up to date definitions. Check your HOST file for any unusual entries as well.
I assume this is the only site you are having problems accessing?