Hi! My iPhone 4 is on 4.3.3 Jailbroken. (Windows Vista 32-bit, latest iTunes) I tried to restore to latest ios 5.0.1. Then I got the following error: 1) When restore normally, got error 21. 2) When restore in DFU mode, got error 1601, 1602. I tried to reinstall iTunes, changing usb port, and used iREB r5 to no avail. What else should I try? Anybody can help me out, will really appreciate it! Updates: I solved it using latest redsn0w, go to extras > fix recovery. From there it will load some commands in iPhone, and voila welcome activation screen, with ios 5.0.1.