Sims 3 Member Login Error: Not Logged In

Hello!
Every time I try to log in, in-game, in the launcher, or on thesims3.com, it will read a red error message above the login that says either "Invalid login information. Please try again." or "Not logged in." I've tried logging in from another person's computer, and it works just fine. Any ideas about what is causing this on only my computer, and how I might be able to fix it?

Thanks.