Have you tried a battery pull?
If that doesn't work then pull the sim and sd card and do
a master reset.
From Howard's Forum.
Tmobile U7519/Tap user lock solution:
1. Turn on the phone and when prompted to enter password enter 1234
2. Press END key twice quickly at the password error screen.
3. Press the dial pad icon.
4. Enter *1673492846 then press the down key on the Dpad
5. Select menu option 8, 1, 1