I don't think they have to be Genuine but just Top Quality not cheapos.

Cheers
Col

EDIT: Having just re-read the opening post, I realise that the vehicle being a 2009 model shouldn't be effected by the below post, but left up in case of any others not known.

It may have nothing to do with this, but the recent recall for RRS within a certain VIN range, is due to faulty Crankshaft Position Sensor and re-program, one of the possible effects of this not having been carried out under recall, is that the engine can cut out, so it is just an outside chance that this may be the fault?

Click on "borrowed" link below:
http://www.rrsport.co.uk/gallery/albums/userpics/10024/P080.jpg John

RRS MY12 SDV6 HSE. Sumatra Black/Ebony & Walnut + Dynamic Pack, + Cold Climate Pack + Memory Pack, Digital TV/DVD, Premium Leather, Cornering Lights, Cooler/Fridge Box, & most Options.