Hello.
I've kernel 2.6.18.2 and newest version (for now) of yaffs2. 
I have these strange messages received via log console:

 stopping tasks timed out after 20 seconds (3 tasks remaining):
  yaffs-bg-1
  yaffs-bg-1
  yaffs-bg-1

And, in a moment : 

Restarting tasks...<6> Strange, yaffs-bg-1 not stopped
 Strange, yaffs-bg-1 not stopped
 Strange, yaffs-bg-1 not stopped
 done

Have you ever had this problem before? I think it's closely related to threads used by yaffs..
Regards