I'm out of luck. I almost followed flipflip instructions but the kernel continues hanging in the same point. This is my environment:
bootcmd=${x_bootcmd_usb}; ${x_bootcmd_kernel}; setenv bootargs ${x_bootargs} ${x
_bootargs_root}; bootm 0x6400000;
bootdelay=3
baudrate=115200
x_bootcmd_usb=usb start
x_bootcmd_kernel=nand read.e 0x6400000 0x100000 0x400000
x_bootargs=console=ttyS0,115200
x_bootargs_root=ubi.mtd=2 root=ubi0:rootfs rootfstype=ubifs
ethaddr=02:XX:XX:XX:XX:XX
ethact=egiga0
eth1addr=02:50:43:df:7a:ca
serverip=192.168.1.10
ipaddr=192.168.1.23
mainlineLinux=yes
arcNumber=2659
stdin=serial
stdout=serial
stderr=serial
Environment size: 498/131068 bytes
I followed the steps to build U-Boot and flash it
here, and my compiled U-Boot it's working.
Then I almost followed the steps
here to build the kernel. Downloaded the kernel, patched it and then executed:
make guruplug_defconfig
make menuconfig
make uImage
I didn't exec the "make-kpkg kernel_image kernel_headers", because make-kpkg isn't installed in my system. Is this step necessary? I suppose it's only to create .deb packages, right? Also I think there's an errata in the instructions, I think the line "make guruplug_config" should be "make guruplug_
defconfig".
The kernel was built, but it doesn't boot

. Could it be the cross-compiler? Where can I download the same version you're using? (I'm using the one automatically built by OpenEmbedded). What else can be?
Edit: There must be something wrong with my plug or with the process I follow. I have updated U-Boot with downloaded flipflip's version:
tftp 0x6400000 u-boot.kwb
nand erase 0x00000000 0x0100000
nand write 0x6400000 0x0000000 0x80000
reset
Then restored my environment and tested downloaded flipflip's kernel:
tftp 0x6400000 uImage
bootm 0x6400000
And the kernel continues hanging

U-Boot 2010.03-01266-g42f7128-dirty (Mai 12 2010 - 13:28:48)
Marvell-GuruPlug (-: flipflip's version 20100512 :-)
SoC: Kirkwood 88F6281_A0
DRAM: 512 MB
NAND: 512 MiB
In: serial
Out: serial
Err: serial
Net: egiga0, egiga1
88E1121 Initialized on egiga0
88E1121 Initialized on egiga1
Hit any key to stop autoboot: 0
GuruPlug>> printenv
bootcmd=${x_bootcmd_usb}; ${x_bootcmd_kernel}; setenv bootargs ${x_bootargs} ${x
_bootargs_root}; bootm 0x6400000;
bootdelay=3
baudrate=115200
x_bootcmd_usb=usb start
x_bootcmd_kernel=nand read.e 0x6400000 0x100000 0x400000
x_bootargs=console=ttyS0,115200
x_bootargs_root=ubi.mtd=2 root=ubi0:rootfs rootfstype=ubifs
ethaddr=02:50:43:e3:83:15
ethact=egiga0
eth1addr=02:XX:XX:XX:XX:XX
serverip=192.168.1.10
ipaddr=192.168.1.23
mainlineLinux=yes
arcNumber=2659
stdin=serial
stdout=serial
stderr=serial
Environment size: 498/131068 bytes
GuruPlug>> tftp 0x6400000 uImage
Using egiga0 device
TFTP from server 192.168.1.10; our IP address is 192.168.1.23
Filename 'uImage'.
Load address: 0x6400000
Loading: #################################################################
#################################################################
#############################################
done
Bytes transferred = 2561944 (271798 hex)
GuruPlug>> bootm
## Booting kernel from Legacy Image at 06400000 ...
Image Name: Linux-2.6.33.3flipflip
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2561880 Bytes = 2.4 MB
Load Address: 00008000
Entry Point: 00008000
Verifying Checksum ... OK
Loading Kernel Image ... OK
OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel.
I'm starting to hate the day I bought my plug

. I should have bought a Beagleboard...