EDIT: nvm. seems the servers are down.... ignore the below... for now at least.
Ok you guys, try this:
go here:(for vista/win7)
C:\Users\<user)\AppData\Local\Ironclad Games\Sins of a Solar Empire\Setting
open up diplomacy.user in a text editer.
and make sure these two lines are this:
IcoServerAddress "ico.stardock.com"
IcoServerPort 6100
If that doesnt work, try deleting that file, the game will regenerate a uptodate one next time it loads.
If none of that works, try a full reinstall from impulse.