Client error 'Please set up an account

A PC running GW 8.03 prompts the user to 'Please set up an account' when they try to launch GW this morning. It's been working fine for months if not years. The GW client works fine for this user on a different PC. I've uninstalled and reinstalled GW but still get the error. I've requested CleanIt from but it hasn't arrived yet. Does anyone have any ideas other than run the cleaner when it arrives?