Let me make sure I understand. Are you getting this message on the phone, or on your PC when you try to connect?
If it's on your PC, do this: In EasyTether, tap Menu / Setup.
WiFi Encryption should be checked. If not, check it.
Tap Encryption setup method, and choose Auto
Tap Change Passphrase, and enter a 13 character string that you can remember, but hopefully isn't too obvious.
Tap Change SSID, and enter a value you can remember. Or leave the default value, if you want, but make a note of it.
Tap the back arrow, and press to start tethering.
Now, when you try to connect on your PC, and it prompts for SSID, enter the value from the phone. Ditto for the security key.