/dev/hdc not a valid block device

[Charles Benett <charles benett1 demon co uk>]

Hi!
When I go to mount a cd (ATAPI cdrom reader), with "mount /mnt/cdrom", I
get:
"mount: /dev/hdc is not a valid block device"
Does anyone know what has happened?

Related info:
The cdrom was working. I haven't recompiled the kernal. This is RedHat
6.1.
The problem started when I installed a SCSI tape drive. kudzu claimed
the cd had disappeared as well as the tape appearing.
In the boot messages, it is finding an ATAPI optical disk on hdc, but
also giving the message:
"hdc: driver not present"
(Which seems odd as I haven't touched the kernal, so how could it have
gone?)

Any ideas?
Thanks
Charles