Install NetBSD amd64 using dk wedges scheme

[Philippe Saint-Jacques <philippe.st-jacques%polymtl.ca@localhost>]

I installed NetBSD successfully in the past on my Macbook Pro (rev 3,1) by 
building an INSTALL kernel with disabled GPT options.

Now, I try to install NetBSD 5.1 using GPT partitionning scheme. I followed the 
instructions given at this page :
http://wiki-static.aydogan.net/How_to_install_NetBSD_on_an_Apple_Macbook_w/core2duo

I now have 2 additional dk wedges on my disk, one for root and swap. I newfs it 
and extracted all the installation sets to it. Here is the GPT layout :
Current GPT partition table:
 #      Start LBA      End LBA  Type
 1             40       409639  EFI System (FAT)
 2         409640     97803751  Mac OS X HFS+
 3       98065896    293378399  Mac OS X HFS+
 4      293642240    342468607  Basic Data
 5      342468608    382333326  NetBSD FFS
 6      382333327    390721934  NetBSD Swap

I also modified fstab to look like this :
/dev/dk4                /       ffs     rw
/dev/dk5                none    swap

I also installed the bootcode :
cp -p /mnt/usr/mdec/boot /mnt/usr/mdec/boot.cfg /mnt
installboot -v /dev/rdk4 /mnt/usr/mdec/bootxx_ffsv2

Finally, when I reboot the machine, rEFIt find my NetBSD installation (it 
displays the option, and the NetBSD icon with it), but when I select it. in 
boots in fact partition id #4 which is Windows. It should normally boot 
partition #5. It doesn't even boot the kernel at the root of /dev/dk4.

Do you know what I could have done wrong during my installation ?