Any browser issues? Log onto secure internet sites etc?
You dont have any older disk games you can fish out? I take it you dont have a 2nd pc you can plug into the router and install Steam on?
People above have mentioned firewall changes. Why not just dissable or uninstall it to get it fully out of the equation?
Failing not being able to gleen anything from the above, bite the bullet and back up all your steam game files and then reinstall steam.
Edit: Not much into mmos recently myself, but I am surprised Rift needs you to be logged into Steam to play it, regardless of whether you bought it on steam or not. Why not download their stand alone client and not use Steam that session.