1) Downgrade back down to 1.1.1. You do this by googling the 1.1.1 ipod touch firmware and downloading it to your computer. Then in itunes with your ipod attached click on update while holding shift and navigate to the 1.1.1 firmware. Then it will restore to 1.1.1
2) Once you have 1.1.1 then you jailbreak
3) Then you install Oktoprep from installer.
4) Then you update to 1.1.2
CHeck here for more... and you might want to search next time...