jffs2 eraseblock size

Hi, 
i compile my kernel for a mini2440 with buildroot. 

I flashed uboot (download from friendly arm), as own generated with
buildroot is not running. (Any Ideas why?)

wrote kernel and jffs2 file system to nand. 
Kernel is booting, but with filesystem something is wrong:

 I get many errors like this:
-----------------
jffscan2_scan_eraseblock(): Magic Bitmask ... not found...
...
Node at ... would run over the end of the erase block

Perhaps the file system was created with wrong 
erase block size?
---------------

Whats wrong here?
Where can I set erase block size in buildroot / uboot ?
and what's the right erase block size?

any ideas?

From here:
http://code.google.com/p/friendlyarm/wiki/Linux_Tutorial

For the older 64M mini2440 . . . -e 16 sets the erase block size used by
mkfs.

mkfs.jffs2 –lqnp –e 16 –r target –o output/my_rootfs.jffs2

I believe all the other machines use the same erase block size but I'd have
to search for it.

Make that:

I believe all the other machines use the same BUT different erase block
size to the 64M machine, but I'd have to search for it.

The erase block size of the 64 MiB NAND part is 16 kiB, all other known to
work NANDs use 128 kiB erase block size.