I have updated to OS 3.0 and jailbreak and unlocked it using redsnow almost a week ago. Everything worked fine until I update the Cydia tonight.

After the update it hanged and I had to restarting it by pressing the power and home button. Now it won't boot up. It shows the Apple logo and after that a black screen will appears.

Does anyone encountered this problem?
Is it safe if I put the phone in DFU and restore OS 3.0 again? I mean can I still unlock it after restoring the OS 3.0?
If not can you please tell me how can I solve this problem?

Thanks.