10.5.5 Update Woes - Is my Mini dead?

Hello kids.

I'm hoping that one of you can help me and thanks in advance to anyone who replies, all input is welcome.

I have a Mac Mini (1.8GHz Intel) and I just tried to update to 10.5.5 last night. Everything seemed to me to go smoothly, it installed and rebooted, but as soon as it booted back up, I was greeted with a gray screen, no apple logo, nothing...

Things I have tried already:
Zapping Pram (ignores keyboard input, doesn't do anything)
Booting from CD (Drive spins up, but kybd input is ignored so does nothing)
Booting into target disk mode (I have a clone of my OS on an external HD so it's thankfully backed up, and it's normally bootable).
Safe Mode (again, kybd input is ignored and this fails miserably)

No key inputs seem to have any effect - it ignores them and stubbornly continues to display the gray screen.
That is to say that I cannot zap pram, boot from CD, or into target disk mode anymore. Neither can I now eject the boot CD I put into the mini.

Googling for this got me a few leads, but nothing solid so far. The closest I have found is this: http://www.macfixit.com/article.php?story=2008091609143937

At this point, I'm considering taking the thing apart and replacing the HD (I bought it 2nd hand, it's well out of warranty and I am handy with hardware replacements, so I am not afraid of breaking it) But I do not know if a blank HD would solve the issue.

Anyone have similar issues? Or care to weigh in with advice? or am I hosed?

thanks again!

I had the same thing happen when I updated my MacBook. However, when the system hung on the blue screen (all it showed was the cursor), I pressed the on\off button and was greeted with the standard "Reboot, Shutdown, LogOff, etc. screen. I chose reboot.

After it rebooted everything came up normal. However, the update broke one of my applications (a hurricane tracker program) and I could not easily bring the MacBook out of sleep to use my external monitor as I had been doing before.

I wound up removing the update (I had made a backup before updating) and now everything is OK.

Regards.

Just a heads up. Are you using the new Aluminum keyboard? There are issues with that keyboard and the Mini at startup and it's not recognized till you are in the OS. Do you have another USB keyboard you can try if that is the case?

AH!!!! yes I *am* using that very same keyboard. I will try with my trusty old saitek and post the results. Thanks to you both for your helpful insights!

Sadly this doesn't seem to resolve the issue. I still cannot get the mini to recognize any boot options by holding keys down. I'm starting to think that the HD might need to be replaced so I can install a fresh copy, but I am not sure if this is a firmware issue or a driver issue.

The main difference i suppose would be that in the case of bad firmware, no new hardware will rescue me. Does this seem to have merit as a theory?

Another update:

I removed the HD and tried booting with NO internal HD (essentially trying to eliminate if it's an issue that resides on the disk or firmware as above stated)

Surprise surprise - same behavior. I am getting a very bad feeling about this, and I really am afraid that I've toasted this thing. Evidently slapping in a new HD and re-installing is not an option, if I cannot even boot it...

Any further advice, even grief counseling would be appreciated.

UPDATE:
I went out and bought an external HDD case to verify if it was the HDD. Drive works fine, and I can at least recover my data on another system. I can now conclusively say that it is NOT the Hard Drive, but rather the Mini ITSELF that was broken by the updates. So the next q becomes what do I do with my busted hardware?