Why is my iPhone jailbroken tethered?

[BlindSoul]

Hello,

I got an iPhone 3GS on Baseband 06.15.00 , iOS 4.2.1 .
And I only success jailbreaking it in tethered jailbreak means if I don't boot it tethered through Redsn0w -> Cydia and Safari would always crash when I want to open them.
Is there anything I can do?

Thank you very much!

 

[Applejuiced]

Run greenpoison to untether.