My iPhone 4 4.0.1 JB done with jailbreakme has been acting wonky for a while, I tried uninstalling a lot of the stuff from Cydia but I still get app crashes. So my plan is to upgrade to the latest firmware (4.2 or 4.2.1?) to unjailbreak it then downgrade back to 4.0.1 and just rejailbreak it. I'm going with this method since I want to preserve my application save data which I would lose during a restore. If there is anything with my logic here, correct me. I have saved my SHSH blobs through TinyUmbrella and when I JB'd my phone the "make my life easy" option in Cydia. I also have a file called iPhone3,1_4.0.1_8A306_Restore.ipsw which is supposed to be the 4.0.1 firmware for iPhone 4's.