@Skittlessimheart I'm not sure why the launcher is intermittently not working for you, but two possibilities come to mind. One is that your password has a special character that the launcher is rejecting; the other is that some file within the Sims 3 user folder is being corrupted.
For the former, try changing your password to something with only letters and numbers. For the latter, move your entire Sims 3 folder out of Documents\Electronic Arts and onto your desktop. Open the launcher to spawn a clean folder and see whether you can sign in. If not, the issue isn't the user files. If you can in fact sign in, try transferring the files inside the old folder to the new one, but leave the contents of Downloads behind, as well as any files in DCCache that don't end in .dbc or .ebc.
