My sons Pismo #1 went grey screen in May. Replaced the logic board. I
powered it up entered the password and it went grey.
I had another working Pismo so put the HD from Pismo #1 into Pismo#2
powered it on entered the password and had the desktop with all icons, I was asked if I
wanted to update software I clicked yes, was asked for a password ,
entered the password and the screen went grey.
So I now have 2 non working Pismos.
Pismo #1 is a 500mhz/80g HD / 767 Ram
Pismo#2 400mhz/ 80g hd/ 1g Ram
Here is what i have tried.

Swapped HD into each Pismo, grey screen.

I put the orig 8 gig HD in ,same thing it was doing with either HD.

Won't go into Target Disk Mode.

Tried resetting PRAM

Tried booting from OS 9.2 -- Grey screen

Tried booting from OS 10.3--Grey Screen

When I booted from Disk Warrior I got the Grey apple screen wasn't
able to get into the program any further

Tried Option power on--- got a blue screen with the rt arrow and
the circular arrow with the clock in the upper left hand corner but
it doesn't go past that screen.

Swapped Ram same grey screen.

After I put #1 HD into #2 ( a working Pismo) it went into this state. Same as #1

Strange thing is after the logic board replacement it booted up but went grey after password was entered. After the 1st swap of HD's it booted up but went grey after password was entered.

Now Pismo #2 won't power on at all.
Pismo #2 won't boot up into anything but the grey screen. Won't boot from a CD or into Target Disk Mode.

Any help or suggestions would be appreciated.
Thank you,

That is pretty strange. I have seen a similar issue with a bad processor causing booting problems like you describe. I would try swapping the processors if you haven't yet.

Regarding what happened to the one that got the software update, I would say it was just a coincidence even though that sounds like a weak answer. I could see a software update kill a hard drive install, but you would still be able to boot up from cd.