Hi Andy and Derek,
and any other D300 user, there is an ongoing thread on
www.nikoncafe.com that if not already seen would be worth reading.
It is in the D3/D300 sub forum and is penned by a Jim Fenton, a respected bird photographer and long time Nikon user, and relates to dead battery/focusing syndrome!!
And yes, I do own a D300, so I am keeping my eye on it.
regards Subzero.