Then hash out the entry that's there and add two new nameservers, so it looks like below:
Save and then retry Synaptic. If the fix works, when you reboot it'll reset, so you need to edit your dhclient.con file to make the fix permanent.
cp /etc/dhcp3/dhclient.conf /etc/dhcp3/dhclient.conf.bak
Find this line in the code.....
#prepend domain-name-servers 127.0.0.1;
and replace it with......
prepend domain-name-servers 188.8.131.52, 184.108.40.206;
(notice I've removed the hash symbol as well as changing the servers).
Next, look for the "domain-name-servers" line, and remove it. The text will look something like this........
request domain-name-servers, subnet-mask, broadcast-address, time-offset, routers, domain-name, host-name, netbios-name-servers, netbios-scope;
Remove the bit that says "domain name servers," making sure you remove the comma too. Save the file and then restart your network. The changes should then hold on reboot.