Non system disk or disk error (was Fix grub)

Not really sure what's happened, but had some funnies so did an update and all seemed ok (except my xbox wouldn't talk to plex) so rebooted.... but it won't reboot, looks like grub is missing or something as disk seems ok. How do I sort/fix/repair the grub?

No bootable media...

Hmmm at a loss disk is there I can boot of a livecd and see everything but not booting from it at all. And all I get when I try a livecd is that the grub commands don't exist. ALmost quicker to just reinstall!

A Picture tells a thousand words (so they say) - So my OMV won't boot, so I created a rescue USB http://www.system-rescue-cd.org/ and booted off of that. I can then mount and view the disk and it looks fine, even reinstall grub and check the boot partition... but still refusing to boot. Any ideas?

I't s HP Gen 8 microserver, first bay is 250gb disk for boot / system then other 3 disks are data (currently removed just in case!!)

So didn't get anywhere with this, so ended up disabling onboard raid... then it worked fine!!! Using software raid anyway so no loss, but still don't know why it changed.