Google DNS servers in Brazil

We have a sonicwall NSA 240 in our office in brazil. The DSL carrier there has our internet over PPoE. The strange thing is that they do not have any DNS servers of their own. They (the DSL carrier) listed Google's DNS servers for use 8.8.8.8 and 8.8.4.4 (we are using IPv4 for LAN).

The problem is that some web sites are available and some sites are not. Completely random. http://globo.com will not load, in a browser (we tried all the big three browsers (FF, IE, Chrome) but other sites like amazon.com.br will load without a problem. All machines are running Windows 7 with the firewall turned off.

I have tried DHCP and static IP. Same result. I have tried it with the wireless AP and with the computer plugged into the 240 via ethernet. Same result.

Everything else on the nsa 240 is factory except the changes that were made to network (LAN and WAN setup) and VPN (for site to site)

We thought maybe it was because the VPN between sites was active, but when when we disconnected the VPN between our US office and Brazil office, and rebooted the brazil office sonicwall, still the same issues were happening. Even when I removed the VPN profile on the 240 for the site to site still we got the same issue.

At this point I am open to any suggestions.

Thanks