I believe that there are known issues with block sizes other than 512.  
Check the mailing list archives; I've seen information about this 
recently on the list.

netbsd@bortal.de wrote:

>Hello list!
>I have already posted this problem to the port-i386 list, but haven't got
>an answer so far.The url is: http://mail-index.netbsd.org/port-i386/2004/08/17/0008.html
>
>I was wondering if anyone here could give me a hint why it fails.
>
>Thanks, Mario
>
>
>
>!DSPAM:41231084281335941284355!
>
>  
>


-- 
Seth Kurtzberg
CQL
480-661-1849
seth@cql.com
CQL - The Open Source Database for Embedded Applications