I'm very sorry for bringing this issue up again, and have trawled through the forums for a possible solution, many of which I've tried, had some success and ultimately failed!
After upgrading my GuruPlug Kernel to 3.2.1 the plug stopped responding (it was at a remote location and done over the internet using flash tools within Debian, worked many times in the past).
When I eventually got hold of the plug and pluged in the UART connector, the boot process got as for as:
Uncompressing Linux... Ok, booting the kernel
I've tried to go back to my previous kernel uImage -no success.
Tried to make a new Kernel image - no success
Tried using the original stock uboot and Kernel - no success
Tried using the latest uboot and flipflip's uboot - no success
Tried using a pre built sheeva linux kernel - boots sometimes (usually straight after a flash) but then goes back to the original problem.
I've followed various guides on this and other websites (ones which I know have worked very well in the past) but they ultimately all fail at the same point.
This last point is really frustrating in that I've fully wiped the plug and gone back to basics, but it still fails (but sometimes boots!!!), there is not logic or hard fault there, really frustrating.
Has anybody got any ideas?
Other than selling this on ebay as a fancy door stop!
Many thanks and sorry for the rant!