64 bit kernel

Hello.

I've upgraded to Snow Leopard from Leopard a couple of weeks ago, and I've read about the 64 bit kernel boot option, but I can't seem to get it to work (Software section in the *System Profiler* says "_64-bit Kernel and Extensions: No_").

Here is a rundown on the tech info of my mac:
% *Macbook Unibody* (bought at early 2009, before it was changed to be the Macbook pro) - MacBook5,1
% The output of "_ioreg -l -p IODeviceTree | grep firmware-abi_" says its EFI64
% I did an upgrade and not a clean install
% I tried holding down the 6 and 4 keys while booting (before the gray screen appeared) and the System Profiler still showed that it's not a 64 bit kernel
% I changed my /Library/Preferences/SystemConfiguration/com.apple.Boot.plist file to have:
*<key>Kernel Flags</key>*
<string>arch=x86_64</string>
and still no 64 bit kernel according to system profiler.
% I installed all the updates from apple (currently at 10.6.2)
% The Extension section in System Profiler lists the following as NOT 64bit:
$ BSDKernel6.0
$ CHUDKernLib
$ CHUDProf
$ CHUDUtils
$ IOKit6.0
$ Libkern6.0
$ Mach6.0
$ System6.0

So - why is it not booting 64 bit kernel, and how can I fix it/make it boot 64 kernel ?

All the tech info shows it should do it (except maybe for the listed extensions which are not 64bit, but there's not reason that they won't be, if I did a normal upgrade to Snow Leopard, the efi is 64, and other users with the same details can boot 64 bit kernel).

Thank you very much for any help!