If you are getting this issue, please try these follow solutions to resolve it:

Reset IP Tables

Create a shell script (iptables_flush.sh) and copy paste the following lines:

#!/bin/sh
echo "Flushing iptables rules..."
sleep 1
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT

Make the file executable
chmod +x iptables_flush.sh
and run the script:
./iptables_flush.sh

(Source: http://insanelabs.net/linux/linux-reset-iptables-firewall-rules/)