>>I did a "eraseall" of the device, but the moment I try to write, it's 
>>all marked bad...
>>Any new hints?
> Make sure that bad block checking in the MTD layer is commented out (it does wipe all the factory marked bad blocks but in my experience this is not a crisis for development work) or the blocks are not erased at all and remain "bad".

Well, the device does report 99% free according to "df" after eraseall.
Further, a "mkyaffs" on the device does not state that there is 
thousands of bad blocks - just the factory ones, so I think eraseall 
does it correct?
Moreover, I tried it on a new NAND device never before being used for 
YAFFS, and the same occured (with my new kernel without YAFFS_ECC)...

You still think I should try without bad block checking?

// Martin