Originally posted by AlphaDenver
More then likely it is a DNS related issue.
Start > Run > ipconfig /flushdns
Then try the website again. Also check your HOSTS file at:
(Open with Notepad)
C:\WINDOWS\SYSTEM32\DRIVERS\ETC\HOSTS
Make sure your website name is NOT in their with any number before it. If it is in there delete the entry and save the file.
I agree with alpha. If it were an admin or virus issue.. using a different proxy would still have the same effect. The fact that if he uses a proxy and it allows him to see the site means he should definitely try flushing the dns to remove any bad dns entries. Or you could wait 24 hours.. dns normally flushes every 24 hours or so.