Try these methods to debug any network or DNS issues you have.
If you on windows the following command will flush the dns cache and hopefully get the correct address.
1. Click - Start
2. Click - Run
3. Type - cmd (command on some systems)
4. Click - OK
5. Type - ipconfig /flushdns
6. Restart your system (if possible) and try visiting the site again.
If this still does not work please contact support performing step 1 through 5 with the output from the following commands:
1. Type - nslookup yourdomain.com
2. Type - ping yourdomain.com
3. Type - tracert yourdomain.com
4. Type - ipconfig /all
5. Type - netstat -a