I have set up an openVPN tunnel on my VPS (OpenVZ - Ubuntu 12.04).
The problem is I can only browse websites which support ipv6 like google.
http://whatismyv6.com/ reports me that I've an ipv6 adress, so I guess this is the problem.

Server configuration:

dev tun  
server 10.8.0.0 255.255.255.0  
ifconfig-pool-persist ipp.txt  
ca /etc/openvpn/easy-rsa/keys/ca.crt  
cert /etc/openvpn/easy-rsa/keys/server.crt  
key /etc/openvpn/easy-rsa/keys/server.key  
dh /etc/openvpn/easy-rsa/keys/dh1024.pem  
push "route 10.8.0.0 255.255.255.0"  
push "dhcp-option DNS 8.8.8.8"  
push "dhcp-option DNS 8.8.4.4"  
push "redirect-gateway def1"  
comp-lzo  
persist-tun  
persist-key  
status openvpn-status.log  
log /var/log/openvpn.log  
verb 3

Client configuration:

client  
remote xx.xx.xx.xx 1194  
dev tun  
comp-lzo  
ca ca.crt  
cert client1.crt  
key client1.key  
redirect-gateway def1  
verb 3  

I have configured NAT with this command: iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to xx.xx.xx.xx
Can someone explain me how I can make it works (forcing ipv4?)
I had the same problem with another vps and I also tried on another client (All Windows 7).