First I was just randomly disconnecting but I figured that it was probably just router and ISP problems after a big storm, but now my router seems to be working fairly well but when I get on Spiral Knights I get on for a few seconds and then I'm disconnected, all further attempts after that leave me at the login screen saying that it can't authenticate with Steam and that I need to make sure my steam client is running and I'm not logged in elsewhere.
Did you get any repairs done on the modem line? I would run a speed test and if your getting less then 90% of your subscribed speed, I'd call up your ISP and have them check it out.