1. There's no 1.20 Firmware upgrade available, so I suppose its 1.10 you are trying to upgrade to?!
2. Did you follow the instructions by Samsung? Place the upgrade file itself in the root directory of the SD-card? Otherwise it will not work.
3. Read carefully the undermentioned thread as it may describe the situation you're in now and give possible solutions...
4. If this doesnot work, contact samsung.com service department and ask for further advise (e.g. where to bring your camera to be serviced)
Best regards and good luck, hope it helps, Marius