i7500 Unlock Button Broken
This happened to me again. The process of unlocking was as follows:
- Call the Android phone from a normal phone
- Pick up the phone
- Press the options button
- Click the button to add someone to the call 
- Press the "go back" button

It should return you to the home page.

After that, setup Pattern Unlock. It only uses the touch-screen, so it works with a broken lock button.