Sounds like you may be verifying the wrong credentials.

Incorrect PlayOnline ID or Password

This is actually a common error. Verify the credentials saved in your POL Client to make sure they are saved properly at the SE AM site. It might be best to login to the site and re-enter them again....carefully paying attention to upper/lower case and such.

Note, this is you original POL credentials we are talking about, that get saved in your local POL client. I'm talking about the funky 4 letter/4 number POL ID issued to you by the system when you first activated your account. Look where that is saved within POL, and make sure you have that info saved correctly at the SE Account Management site.

You never enter this information during login, as it is saved within the client and saved within your profile at SE AM. They get passed in the background when you enter you SE ID and password/token. If this portion is not in synch, you get the message about incorrect POL ID and/or password. The key thing there being your POL ID, and not your SE ID. Make sure that is entered/saved properly.