Most definitely.. PRAM holds all kinds off settings and stuff. Couldn't hurt to put it in there.

It sounds like you're ready for one of these...
The Wheel

Boot from an install DVD. That will tell if it's hardware or software.

If the keyboard isn't responding C may not work so you'll need to mouse around to the Startup Disk preferences to set the DVD as the boot device. If the keyboard won't open the tray you'll need to hold the mouse down at startup to open the DVD tray.

OK, third times a charm.
Sort of.
As a last ditch effort, I decided to do an Archive and Install.
Big mistake because it asks for a password at login.
No keyboard, no login.
I called Apple help last night, and they've never heard anything like this.
I love setting a precedent!
This morning I brought home an Apple aluminum keyboard aaaaand: It worked!
BUT, the login keeps rejecting my password.
Multiple attempts to boot from the DVD failed.
It keeps ejecting the DVD at startup, even when holding down the C key.
Maybe I should do a PRAM reset?
Any suggestions?

Is it the correct DVD for that machine? It seems it may not be. Is it the one that came with the machine? Going to need some details. What machine is it exactly. What kind of install DVD is it. The DVD should have a version number and date on it.

Did you follow my instructions above for booting from the DVD?

If the keyboard isn't responding C may not work so you'll need to mouse around to the Startup Disk preferences to set the DVD as the boot device. If the keyboard won't open the tray you'll need to hold the mouse down at startup to open the DVD tray.

You won't need to enter a password to do that, as long as the Startup Disk prefs aren't locked.

One last thought, have you tried another mouse? Maybe it's fubarring the keyboard commands. Set the startup disc like I mentioned above then immediately unplug the keyboard and mouse after you restart.

Wonder if it would see the keyboard then.

PowerMac G5 dual1.8.

I'm using the Leopard install DVD, which worked a couple days ago.
I'm sure I still have the original discs that came with the computer, just need to fine it. I'll try that next.
Can't choose a startup disc, since the only thing that comes up is user login asking for password.
Maybe boot into Safe Mode?

Okay, sorry, you did mention the machine earlier on, it got lost in the shuffle.The Leopard should boot it. The optical drive was okay?Couldn't hurt, hopefully it sees the Shift key.

I see, so only the log in screen is coming up. So you haven't been able to boot past that this whole time.

As far as the PMU or SMU, the first gen dual 1.8 had a PMU. http://support.apple.com/kb/HT1939

The second gen had an SMU http://support.apple.com/kb/HT1436

You can try doing an fsck http://support.apple.com/kb/TS1417 to repair the disk, but that involves a working keyboard.

How about... FWTD mode and run disk repair on it.

Target disk mode is another good idea. Either put the G5 into TD mode and see if its hard drive can boot another machine and the keyboard can work, or TD another machine and see if it can boot the G5 and have the keyboard work.