Strange inconsistency

[Stephen Masterman <floyd@animals.mit.edu>]

I'm trying to mount my IDE CD-ROM drive (its a NEC) and I am getting the
following strange inconsistency:

# mount -t iso9660 -r /dev/hdb /cdrom
mount: fs type iso9660 not supported by kernel
mount: [for the supported filesystem types, see /proc/filesystems]
# cat /proc/filesystems
        minix
        ext2
        msdos
nodev   proc
nodev   nfs
        iso9660
# 

proc says I DO have iso9660 support.  And when I recently recompiled the
kernel, I definitely told it to include support for iso9660.
Am I missing something?  I assume I can refer to my CD-ROM as /dev/hdb since
the only other fixed disk is the first IDE hard drive (not partitioned), 
/dev/hda.  Does anyone know what could be happening here?

Thanks