If the enterprise activation screen on the blackberry comes up with and e-mail or password incorrect this means that the initial ETP e-mail has arrived correctly but you have put in the one-time Enterprise Activation password wrong.
How exactly did you initiate the Enterprise Activation on the BES Server?
Also, make sure, you have gone through these troubleshooting steps:
KB13852-Identifying and troubleshooting issues with the Enterprise Activation process