I got similar - hid my GB root with voodoo rootkeeper before doing OTA. The update d/l was fine but failed to apply correctly (crapped out midway leaving my GB install OK). Don't know why but I tried again and this time it seemed to work but after it finished and rebooted, it stuck on the samsung logo. I downloaded the UK CPW 4.0.3 firmware and used PC Odin to apply it - all ok and it restored/upgraded all my apps and data etc automatically. I then re-rooted using cwm.zip and su_busybox_installer.zip and I'm all rooted & booted.