whm can't start...

This is not a WHM problem but one with filesystem. Looks like the CD/DVD is missing (hdc). Try to put it and reboot. If doesn't work, type your password, mount root partition, edit /stc/fstab and comment the line for hdc1

 

You have created LVM partitions which seem to have gone bad. Login to the server from the 'Maintenance' mode and do a File System Check on those partitions. If you are unable to login via the Maintenance mode, you will have to login from Rescue mode using a CD.

Also make sure you don't have any extra entries in /etc/fstab file else the system will try to mount them at startup and since the partitions are not available, the bootup will fail with errors.

 

I am seeing this on some of my customers' VPS servers as well.

I tested it on a new installation of cPanel on a CentOS 5.5 VPS running on a KVM host.

There is no hdc device in the guest's configuration, but when I go into WHM and click Format/Mount a new Hard Drive under Disk Drives, it shows that it found a drive hdc.

If the user clicks the button to Partition, Format, and Mount that drive, WHM will place an entry in /etc/fstab and the system will not boot from then on until the entry is removed.

Is there a way to fix WHM so it does not show this fictitious drive?

 

You should put in a ticket or bug report for this issue, it does nto sound like it happens on all machines but if you can give them a server that can reproduce it they may be able to track it down quicker.