Nikon D50 Autofocus issue

[Frik]

My D50 seems to have developed an intermittent autofocusing fault. A lot of the time it won't find a focus and continues to hunt when set to the central focusing point of the matrix. If I choose one of the other focusing points it seems to focus fine. The issue is lens independent.

Has anyone seen a similar issue and/or have experience of Nikon's repair service? It's out of warranty, obviously.