Thought I'd add my 2 cents...

I just got an N800. I updated to the latest firmware (4.2007.26). I bought this A-Data 8gb SDHC (Class 6) card from newegg: http://www.newegg.com/Product/Produc...82E16820211180

It worked just fine as a FAT32 card in either slot. I tried to use it to boot from mmc using the tutorial here (and elsewhere). I tried various partition sizes for the DOS and the ext2 partitions. I tried both FAT16 and FAT32 for the DOS partition. Nothing worked. I could copy the root filesystem over just fine, and even mount it and see the files. But when I tried to boot from it, it would fail and then boot to internal flash. I also tried updating the kernel to the patched version that allows for faster access to the mmc cards. No difference.

Then I tried this Transcend 4gb SD card from newegg: http://www.newegg.com/Product/Produc...82E16820163159

I made the DOS and ext2 partitions the same size (approx 1.9G) and formatted the DOS partition FAT16. NOW I was able to successfully boot from the internal mmc card.

So, I don't know WHY the 8gb SDHC card didn't work. I think I saw one report of another user getting an A-Data 8gb SDHC to boot, but perhaps he/she had a different model (maybe Class 2?). Anyway, I'd be interested to hear if others have had success with other brands of 8gb SDHC cards. For now I guess I'll have to stick with the 4gb SD card.