NetBSD bootloader randomly boots wrong kernel

[Sad Clouds <cryintothebluesky%googlemail.com@localhost>]

Hi, I'm running NetBSD-5.1 on x86_64, I have the following kernels under /

/netbsd
/netbsd.old

I was supposed to delete /netbsd.old, but forgot about it. I recently noticed 
that NetBSD bootloader would occasionally boot /netbsd.old kernel, even though 
it has not been set up to do so.

atom$ cat /boot.cfg
menu=Boot normally:boot netbsd
menu=Boot single user:boot netbsd -s
menu=Disable ACPI:boot netbsd -2
menu=Disable ACPI and SMP:boot netbsd -12
menu=Xen:load /netbsd-XEN3_DOM0 console=pc;multiboot /xen.gz dom0_mem=1024M
menu=Drop to boot prompt:prompt
default=1
timeout=5

The reason why I know it boots /netbsd.old is by looking at logged kernel 
messages, which tell you the date when the kernel was built

This is /netbsd kernel:
NetBSD 5.1_STABLE (GENERIC) #0: Mon Nov 29 19:52:01 GMT 2010

This is /netbsd.old kernel
NetBSD 5.1 (GENERIC) #2: Fri Nov 19 11:28:39 UTC 2010

Can anyone explain why my bootloader does this??