synaptic package manager wont open

so basicly the title says it all, no error msg or anything. thats probably just the biggest issue i have, when i try to update my computer through the update package thing (sry, a bit slow on the linux lingo) it freezes and then my internet shuts down. i am at a point where i have to do upgrading through a terminal window. Also, when i do that and type in the first command "sudo apt-get update" i get this msg before it starts

*****@*****'s Laptop:~$ sudo apt-get update
sudo: unable to resolve host *****'s Laptop

so i duno if that has anything to do with it but yeah, just trying to give as much info as i can think of...,
oh and i also have changed the network hosts name too prior to the problem starting