HAL is no longer part of Ubuntu, as of 10.04. Mint may still use HAL which
is still in the repositories of Ubuntu, but it has been replaced.

Thanks for the information about Ubuntu and HAL which you say is no
longer used in Ubuntu and has been replaced but you don't say what has
replaced it or what may be causing my optical drive not being found by
either Brasero or K3B.Would a fresh install sort out the problem?Does anyone
else have any ideas?

It was replaced with Devicekit. This was done to speed up boot time.

See:
www.linuxpromagazine.com/.../Ubuntu-10.04-Alpha-2-Removes-HAL

If you run Administration/sysinfo and click the Storage tab, does the DVD drive
show up? How recently was the DVD drive working, and under what environment? It
almost sounds like the device is not plugged in, either the data cable or the
power cable.

What do you mean by "blank then burn"? Do you have DVD-RW media?

I did a clean reinstall of 10.04 and its working again!