problems with setting kern.maxdsiz in /boot/loader.conf

[Alan Jay]

I am running 5.4 RC4 and rebooted today after changing one of the boot-time
variables (maximum data size) in /boot/loader.conf.  I took it from 512MB to
2GB of RAM in order to improve the MySQL performance on the server.

However, upon reboot, the following error comes up:

Fatal trap 9: general protection fault while in kernel mode cpuid = 0; apic id
= 00
instruction pointer     = 0x58:0x8bc
stack pointer           = 0x10:0xf80
frame pointer           = 0x10:0x0
code segment            = base 0xc00f0000, limit 0xffff, type 0x1b
                        = DPL 0, pres 1, def32 0, gran 0
processor eflags        = interrupt enabled, resume, IOPL = 0
current process         = 0 (swapper)
trap number             = 9
panic: general protection fault
cpuid = 0
Uptime: 1s

I tried resetting kern.maxdsiz backto 512MB by pressing 6 at the boot menu and
doing:
	unset kern.maxdsiz
	set kern.maxdsiz=536870912
	show kern.maxdsiz
    - this did not have any effect - exactly the same thing happened again.

Is the kern.maxdsiz now being reset or being reset by /boot/loader.conf after
changing things in the loader does anyone have any ideas.

Nothing else has changed on the server which is being prepared for use at the
moment and was updated to 5.4 RC4 just a few days ago but which has been
running fine and rebooting fine since then until this change.

Any ideas?

Thanks in advance

Alan

PS I assume the only way to remove /boot/loader.conf is to use the 2nd CD set
in fixit mode and remove / edit the file after mounting the root partition.