Why are you on a tethered jailbreak? If you upgrade to 3.1.3 (ONLY if you don't need to unlock), then just jailbreak with Spirit, and it's a REAL jailbreak without the reboot problems. It's an UNtethered jailbreak.
And as long as you don't need to unlock, I'd recommend upping to 3.1.3, ten jailbreaking with Spirit. It will liberate your jailbreak experience tremendously.
