Mac Pro, Lion won't boot

I've tried everything, short of lugging it to an Apple Shop.

it won't get to the login screen.

The boot disk is fine - I connected to it via target mode and 'repaired' it.

I've fsck'd it, reset PRAM and SMC.

I've removed all peripherals and tried safe mode.

it is booting cos I can login to my shares via the local network, but the machine itself won't boot from an external drive, a USB install disk, the original Leopard dvd etc.

All I'm getting is a mouse cursor on a grey screen.

The volume keys on the keyboard work.

Verbose mode doesn't help.

I've done short and long AHT tests and both report *no problem*

and this all started when it froze while playing music in iTunes.

Suggestions welcome.

I've decided that it must be a Graphics card issue, so I've ordered a replacement.

Will report back.

Weird issue, but as you say sound is okay, USB keyboard and mouse all work fine, a mouse cursor on the screen is active and all the disks are accessible and AHT tests all pass.

We shall see.

Thanks!

It was the graphics card.

I fitted the  ATI Radeon HD 5770 1024 MB as several sources say it works with the Mac Pro 1,1 and it does.

My system booted fine to an install DVD, then I put the boot disk back in and that booted fine too, momentary weirdness on reboot when the screen went off and I had to sleep and wake the machine to get it back.

Now the only downside is intermittently it loses sync and the screen fills with sparkling snow - recycling the power to the screen (A Dell 30") resolves that.

Apparently this is a known issue with early Mac Pro and the ATI using DVI output.

I'll have to consider a new screen at some point.

Hope this helps someone.

:)