My ipod touch only goes to the apple logo then freezes, how can i fix this?!?

Basically I have an Ipod touch that is jailbroken with summerboard or winterboard. (not positive which one) but about a month ago I wanted to delete everything off my ipod and format it. So i did that and now it only turns on to the apple logo and freezes. It doesn't go past that. any idea's on how i could possibly fix this?