Odd one indeed Mark. You're 100% sure there's no other symptoms going on? No warning messages flash on the DIC? It's not uncommon for 2005-06's to have wiring connection issues on the electric assist power steering that throws such a load on the system, strange things will happen. Other than that, I'd check for ~14VDC across the battery with the car idling. Less than 14 and the car will basically be INOP. I've seen batteries get tired in as little as 3yrs/80Kmi.
Joel