Please check -
Originally Posted by Dibyajit
..and see if there is a line "system-ca-certs=true". If there is, you need to change it to "false" -
sudo cat /etc/NetworkManager/system-connections/<your connection's name>
Recheck with the first command to make sure it changed to "false", then try connecting again.
sudo sed -i '/system-ca-certs/ s:[Tt]rue:false:' /etc/NetworkManager/system-connections/<your connection name>
Although it does not change the matters with wifi, it is highly recommended to do a proper installation, not WUBI. WUBI breaks often with a potential loss of data (within the Ubuntu virtual disk).