mount_udf: Cannot mount /dev/cd0a on /mnt: Operation not permitted

[raymond.meyer%rambler.ru@localhost]

I do the following to create UDF filesystem on DVD+RW disk:

mmcformat -F -w /dev/rcd0c
...

newfs_udf /dev/rcd0c
Formatting disc compatible with UDF version 201 to 201

UDF properties       014<REWRITABLE,SPARABLE>
Volume set          `0a007d7c5310cdd7'
Primary volume      `646ef20f`
Logical volume      `anonymous`

Total space on this medium aprox. 4589600 KiB, 4482 MiB
Free space on this volume aprox.  4572262 KiB, 4465 MiB

But when I try to mount it I get the following:

# mount_udf /dev/cd0a /mnt
mount_udf: Cannot mount /dev/cd0a on /mnt: Operation not permitted

# mount_udf /dev/cd0c /mnt
mount_udf: Cannot mount /dev/cd0c on /mnt: Operation not permitted

I have

file-system     UDF 

uncommented in kernel config file when I build custome kernel and
disklabel reports:

# disklabel /dev/cd0c
...

3 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:   2295104         0    ISO9660       0             # (Cyl.      0
-  22951*)
 c:   2295104         0    ISO9660       0             # (Cyl.      0
-  22951*) 
disklabel: boot block size 0
disklabel: super block size 0
disklabel: partitions a and c overlap

This is NetBSD-5. Any ideas?