Hi Pete,
Personally, I don't think your hardware is broken, based on the printouts you've been sending.
Since you seem to be at the point where you're just about ready to try and get a replacement, why not try this 'reset to factory defaults' approach?
http://www.openplug.org/plugwiki/index.php/Factory_Default_u-Boot_EnvironmentLet me know how that goes.
-bill