Can anyone enlighten me on what this error means, and how it can be fixed.
This error is displayed, when even it attempts to read a disk.

what type of h/u are you talking about ??

What sort of disc's are you trying to play

A deck that cant read mp3 cd's wont be able to read the discs and will display an error message.

The headunit is a stock radio/cd player for a tj series 2 executive, not aftermarket. All the cd's ive tried have all been non mp3 cds. I believe it's an unreadable problem, as in with the headunit itself. Laser cleaning kit maybe?

maybe its time to upgrade to something with usb and flash?

Sometimes head units just die. It sounds like it is up to replacement age anyway.