[Sony Tablet S] -16-:
Thanks for the quick answer. I just tried that but I get this message:

"E:Prohibit update as a result of checking version or base sku"

Here my recovery.log:

Starting recovery on Sat Dec 8 14:27:17 2012
can't open /dev/tty0: No such file or directory
framebuffer: fd 3 (1280 x 800)
recovery filesystem table
=========================
0 /tmp ramdisk (null) (null) 0
1 /configs ext2 /dev/block/mmcblk0p1 (null) 0
2 /system0 ext4 /dev/block/mmcblk0p2 (null) 0
3 /system1 ext4 /dev/block/mmcblk0p3 (null) 0
4 /cache ext4 /dev/block/mmcblk0p4 (null) 0
5 /misc emmc /dev/block/mmcblk0p5 (null) 0
6 /staging ext4 /dev/block/mmcblk0p6 (null) 0
7 /blflags ext4 /dev/block/mmcblk0p7 (null) 0
8 /datapp ext4 /dev/block/mmcblk0p8 (null) 0
9 /log ext4 /dev/block/mmcblk0p9 (null) 0
10 /data ext4 /dev/block/mmcblk0p10 (null) 0
11 /vsdcard vfat /dev/block/mmcblk0p11 (null) 0
12 /sdcard vfat /dev/block/mmcblk1p1 /dev/block/mmcblk1 0
13 /boot emmc boot (null) 0
14 /recovery emmc recovery (null) 0
15 /system ext4 system (null) 0
16 /vendor0 ext4 /datapp/vendor/vendor0.img (null) 0
17 /vendor1 ext4 /datapp/vendor/vendor1.img (null) 0

Command: "/sbin/recovery"

ro.secure=1
ro.allow.mock.location=0
ro.debuggable=0
persist.sys.usb.config=mtp
ro.build.id=TISU0124
ro.build.display.id=TISU0124
ro.build.version.incremental=120914043
ro.build.version.sdk=15
ro.build.version.codename=REL
ro.build.version.release=4.0.3
ro.build.date=Fri Sep 14 04:41:30 JST 2012
ro.build.date.utc=1347565290
ro.build.type=user
ro.build.user=integ-build
ro.build.host=build5
ro.build.tags=test-keys
ro.product.model=Sony Tablet S
ro.product.brand=Sony
ro.product.name=SYS_001
ro.product.device=nbx03
ro.product.board=nbx03
ro.product.cpu.abi=armeabi-v7a
ro.product.cpu.abi2=armeabi
ro.product.manufacturer=Sony
ro.product.locale.language=en
ro.product.locale.region=US
ro.wifi.channels=
ro.board.platform=tegra
ro.build.product=nbx03
ro.build.description=SYS_001-user 4.0.3 TISU0124 120914043 test-keys
ro.build.fingerprint=Sony/SYS_001/nbx03:4.0.3/TISU0124/120914043:user/test-keys
ro.build.characteristics=tablet
ro.opengles.version=131072
wifi.interface=wlan0
ro.ethernet.interface=eth0
ro.ethernet.autoEnable=yes
rild.libargs=-d /dev/ttyACM1 -i rmnet0
windowsmgr.max_events_per_sec=120
ro.tether.denied=true
ro.sony.sound.enabled=true
ro.sony.display.release=release5
ro.product-res-path=vendor/framework/SemcGenericUxpRes.apk
ro.sony.autovolume.threshold=10
ro.sony.update.server=info.update.sony.net
ro.sony.update.category_id=ST001
ro.config.notification_sound=OnTheHunt.ogg
ro.config.alarm_alert=Alarm_Classic.ogg
drm.service.enabled=true
dalvik.vm.heapstartsize=5m
dalvik.vm.heapgrowthlimit=48m
dalvik.vm.heapsize=256m
ro.sony.wifisleep=0
ro.semc.xloud.supported=true
ro.somc.clearphase.supported=true
ro.setupwizard.mode=DISABLED
ro.com.google.gmsversion=4.0_r3
ro.com.google.clientidbase=android-sony
dalvik.vm.dexopt-flags=m=y
net.bt.name=Android
net.change=net.bt.name
dalvik.vm.stack-trace-file=/data/anr/traces.txt
ro.sony.wan.ipv6.enable=false
ro.sony.dlna_dms.enabled=false
ro.somc.social_product_model=PRODUCT_MODEL_TABLET
ro.sony.irremote.protocol_type=1
ro.sony.ols.eula=0
ro.factorytest=0
ro.bootmode=unknown
ro.baseband=unknown
ro.carrier=unknown
ro.bootloader=0x00000008
ro.hardware=nbx03
ro.revision=0
init.svc.recovery=running
init.svc.nfx_daemon=running
init.svc.radbd=running

I think I found the problem but not the solution...I don't have any region.prop. I have root access, so can I push a region.prop? And if, where do I find the right one?