devfs error on RELENG_5_2

Hello,

I'm running a RELENG_5_2  box and I'm trying to use the devfs to change the
file permissions on
/dev/ttyd1.  After perusing through the man page, I tried to change the
permissions by doing this

# ls -ol /dev/ttyd1
crw-------  1 root  wheel  -  28,   1 Jan 15 20:47 /dev/ttyd1
# devfs rule add path ttyd1 mode 666
devfs rule: ioctl DEVFSIO_RADD: Input/output error
# ls -ol /dev/ttyd1
crw-------  1 root  wheel  -  28,   1 Jan 15 20:47 /dev/ttyd1

but it fails and I'm not sure why.  I'll have to do 
devfs rule applyset if the rule add succeeds since the node /dev/ttyd1 
has already been created but I haven't got that far yet...
I've also tried using the example in the man page
with /dev/speaker, but it also fails with the same error.

# ls -ol /dev/speaker 
crw-------  1 root  wheel  -  26,   0 Jan 15 21:24 /dev/speaker
# dmesg | grep speaker
speaker0: <PC speaker> at port 0x61 on isa0
# devfs rule add path speaker mode 666
devfs rule: ioctl DEVFSIO_RADD: Input/output error
# ls -ol /dev/speaker
crw-------  1 root  wheel  -  26,   0 Jan 15 21:24 /dev/speaker

Any thoughts on this would be greatly appreciated.
Thanks,
John