I am not an expert...
The workaround just worked, but I don't know whether "00000692 Marvell RD-88F6281 Reference Board"
is a valid machid for the sheevaplug, instead of the 'original' 00000831.
At the beggining it worked, but now I have a problem: the sheevaplug ethernet subsystem does not work well...
It does not get an IP by DHCP and assigning a static one does not work either...
I suspect that is caused by the workaround but I don't know.
So I do not recommend doing the procedure/workaround of changing machid,
as it may be unsafe and I warn thay may damage the hardware.
I hope Martin's solution will work... Where will you post the kernel image?