Jordin Red,
Couple things to make sure of.
1. You need to have two accounts.
2. You need to use TSO.exe first to patch to what ever city you are going to (Test Center 3 or The Sims Online)
3. Once you have fully updated and have fully logged into the city of choice using TSO.exe then you can use TSOClient.exe. (Create a shortcut to TSOClient.exe) You will need to use your 2nd account to login
4. If you are running the game from the same location on disk then you must be logged in with both accounts to the same city. (Or at least cities that require the identical version of the Client)
Cheers,
Lee