2.6.29 is not a kernel Debian ships, so it's probably a vendor kernel. Since they ship a kernel that doesn't work on their hardware, you should complain to them.
However, it would be nice if you could confirm that Debian's 2.6.32 kernel works.
Well, I don't have an eSATA plug so I cannot test why the NewIT uboot doesn't work with debian-installer, although I thought that this worked for other people. I'll wait for someone with an eSATA plug to figure out what u-boot works and then I'm happy to update my page. I'll then also fix the contradictions.
I reinstalled everything using your updated tutorial. I still get the same error message. The Sheeva does like my hard disk. I tested the ESIA installer and it worked (out of the box). The big difference is using another (older) uboot version (uboot-sata-090903.bin from NewIT). But with this version your installer won't work (I've already tried that).
Yeah you'll definitely need an uboot with SATA support. So you're saying that with uboot-sata-090903.bin the Debian installer doesn't work? What's the problem exactly?
SATA max UDMA/133 ata1: SATA Link down (SStatus 0 SControl F300) ata2: link is slow to respond, please be patient (ready=0) 2 SRST failed errorno = -16 limiting SATA link speed to 1.5GBps
Maybe it doesn't like your disk... I don't know. Can you boot the whole log?
If you're already running Debian on your eSATA SheevaPlug but you installed as a regular SheevaPlug to USB or SD and you'd like to use the eSATA, then make sure you're the latest kernel from Debian squeeze (apt-get update; apt-get dist-upgrade; flash-kernel), reboot and type this in u-boot:
setenv arcNumber 2678 saveenv reset
Your machine will then be recognized as an eSATA SheevaPlug