I seriously think there might be something with this tool... I just got a brand new XZ, device still locked, official 4.2.2 installed, rooted. Ran V9.3, it hanged on the Backup, I waited for 20 mins, tried again, nothing.
I tried to reboot the device - No response whatsoever, won't turn on, PWR + VOL UP won't work even when held for a whole minute (I tried!). The Led doesn't work either. SUS won't recognize the device at all, no matter the button combination.
Flashtool seems to claim there's a device in Flashmode (No matter the button combination) - But is unable to flash anything, no matter what it is (Tried to flash NUT's stripped 423 ftf, and full stock 423 ftf) - Just gives an error.
It's a brand new device, there's no logical reason to believe anything else besides this could brick it. I wasn't flashing anything at all while running Backup TA, this was after 2 succesful reboots. No other ADB processes were running (Otherwise Backup TA wouldn't have worked). I'm 100% sure I have no malware or viruses on my computer. There's not a chance I could have any on the phone, I barely even got to install a few apps from the market and didn't upload any files to it whatsoever.
Are you 100% it's not writing anything to the TA partition or changing it in someway when it tries to back it up?