Controller Error on CD ROM

My vanilla CD-ROM is slave to a Plextor 708A DVD writer. Both are
connected on the primary IDE connector on an Asus PG5D1 motherboard.
The DVD works fine but the CD-ROM cannot read data even though it is
recognized by the system.

Event Manager says:

IO_ERR_CONTROLLER_ERROR
Message: The driver detected a controller error on %1.

Any ideas on how to remedy the situation? I've replaced drives and
cables and the Device Manager says the CD-ROM is working fine.

Should I chain the CD-ROM as a slave to a hard drive instead and chain
the DVD as slave to a second hard drive and put those into a Secondary
IDE connection?

Any help gratefully appreciated.

Neal Lavon
Takoma Park, MD
USA