I have jailbroken my iPad, but I noticed that I couldn't boot my iPad when I installed some apps, so I removed them, still had to use redsn0w so no luck with booting up iPad without redsn0w.
Then I decided to do a restore, I inserted the file in iTunes and it keeps "preparing" for a while, then says error 1604 and fails.
Now can't seem to start up my iPad anyway.
Could delete this topic or leave it, because I will leave details how I fixed it.
I'm not sure what fixed, but this is what I did:
Tried to restore, failed with 1604 or 1602
Downloaded iTunes update (just came out), still failed
Downloaded RegCure, still failed
Tried to restore with iTunes 20 times, still failed
Plugged in to a different USB, still failed
Tried 21 times to restore, success!
It seams that after few times without leaving Recovery Mode it does work.