having introduced kernel 2.6.9-67.0.4.EL as an update from 2.6.9-5.EL
when rebooting automatically the message
" kernel panic - not syncing: no init found. Try passing init= option to kernel"
is displayed

if we then select the old kernel to reboot the machine reboots ok

are there any obvious differences between the 2 kernels which could be causing this problem?

There's always differences between kernels. There's obviously something wrong with this updated one for your hardware. I'd suggest a few things:

1. Do you need a kernel upgrade? Is there something specific going from 2.6.9-5 to 2.6.9-67 that you need?
2. Don't always assume you need a kernel upgrade just because your updater says you need to update.
3. If it's not broken, don't upgrade.
4. Upgrade if there's a particular security update in which a vulnerability might affect you and your machine.

Now go read the changelogs to determine if you really need to upgrade the kernel. And if you feel you do, then proceed.

thanx for that trickykid.
where exactly on the website would I find the changelogs to get the info required?