can you check your hosts file?
its in C:\Windows\System32\drivers
it called "hosts"
open it with notepad (you are going to have to first open notepad with admin privileges and then open that file) and you should see a bunch of addresses...
delete them and that should allow you to update...
delete everthing after this part
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost