I contacted ZTE and their responce was: 'For your problem, please contact your dealer to check the handset.
If the shop willing to swap a new one for you,you can try to use it,if any problem you can consult us.'
I have mine for around three weeks and it has shut down no more than 5 times. This seems like a minor problem but I'm not happy about it. I'm gonna have it replaced I guess.
Has anyone tried to root the phone and install gingerbread?