Vauxhall astra sri 2007

Does anybody know if the following is a common fault to astras.
The car is a brand new astra.

Open drivers door & get a pinging noise, on dash the amber immobiliser light flashes & car will not start.
This seems to be an intermittant fault & vauxhall are saying it was down to the key code. Had the key changed but the fault has started happening again.
Sometimes if the key is put into the ignition & turned then the horn is pushed once, the immobiliser light goes out & the car will start (this doesnt always work).

Any ideas ?
Thanks