I posted this yesterday. Same thing happened to me.
Im a verizon user running 4.2.8 and i used Jailbreakme 3.0 and it caused my phone to sit at the apple logo for a good 40 min when ever i need to reboot or power off the device, and then when it did load up the unlock screen it was frozen there.. so i had to restore in itunes.
I wish i just kept my GreenPoison JB when i was on 4.2.6.. but i figured this was supposed to be good and went ahead and restored and upgraded to 4.2.8.
Big mistake lol. Oh well. Stock isn't too bad.. dont wanna keep it stock for too long though.
Be warned though, if you haven't restored it already it will keep sitting at the apple logo frozen everytime.. i tryed it 3 times while JB and each time it never corrected.
And you can't just JB with Snowbreeze? It's designed for 4.2.8 and works fine on my phone.
I used redsnow.