My Iphone 3g was on 3.1.2 so I jailbroke it used instalus and downloaded lots of aps, when iso 4 came along I updated to the hacked version and all was well now I have started having problems using cydia and dtunes saying cant write to whatever file and crashing. I think its probably my fault I have messed with loads of stuff but now i would like to get it working right any ideas how I can restore it back to standard and start again without losing the ability to jailbrake it again.