Kernel 2.6.9 -681 missing DVD drives

[Neil Marjoram <n.marjoram@xxxxxxxxxxxxxxxxxx>]

I have just installed the latest kernel and found that when booted the 
system can not see either of the two DVD drives installed.

When booting with kernel 2.6.9 667 I have no problems (678 does not boot 
so I have not tried this.)

The boot log shows these entries :

kernel hdc: _NEC DVD_RW ND-1300A, ATAPI CD/DVD-ROM drive
kernel: hdc: ATAPI 40X DVD-ROM DVD-R CD-R/RW drive, 2048kB Cache

Buffer I/O error on device hdc, logical block 3157894
kernel: hdc: command error: status=0x51 { DriveReady SeekComplete Error }
kernel: hdc: command error: error=0x54

Can anyone suggest a reason for this ?

Thanks,

Neil.