I have found a fix for this problem, as it happened to me too. The way to fix it is once the servers are deleted, do not edit your server list at all, and go into .minecraft and find the servers.dat_temp file. Right click it and copy it so that you have the original and a copied version of it. Then, right click the copied one, and change it's name to servers.dat. Then, refresh your server list and all the servers you previously had should come back. Worked for me!
Wessam Allami
I have found a fix for this problem, as it happened to me too. The way to fix it is once the servers are deleted, do not edit your server list at all, and go into .minecraft and find the servers.dat_temp file. Right click it and copy it so that you have the original and a copied version of it. Then, right click the copied one, and change it's name to servers.dat. Then, refresh your server list and all the servers you previously had should come back. Worked for me!