Caps lock button issue

THE SAME THING HAS HAPPENED TO ME. THE GREEN LIGHT ON MY CAPS LOCK WILL NOT GO OFF. IF I TRY TO DEPRESS IT IT DOES THIS: 4rfv,4rfv,4rfv. IT ALSO REDUCES THE VOLUME ON MY SPEAKERS! IF I PRESS THE NUM LOCK KEY, HOWEVER I CAN TURN OFF THE GREEN LIGHT ON MY CAPS LOCK KEY. THE PROBLEM THEN IS THAT I CAN'T TYPE LETTERS! THIS WEIRD BEHAVIOUR SEEMS TO HAVE OCCURRED FOLLOWING THE CONNECTION OF MY G4 POWERBOOK TO A DATA PROJECTOR, ALTHOUGH THIS MAY NOT BE THE ROOT CAUSE. I ALSO NOTICE THAT WHEN I START UP - DESPITE THE SCREEN RESOLUTION BEING BACK TO 1280 X 854, IT DISPLAYS A RATHER FUZZY LOOKING LARGE APPLE ON THE GREY START UP SCREEN. MY PROBLEM OCCURS WITH EVERY START UP, NOT JUST NOW AND AGAIN. I HAVE TRIED VERIFYING PERMISSIONS AND ALSO DONE A "SAFE" START UP, BUT THE PROBLEM IS STILL THERE. IT DOES NOT HOWEVER OCCUR WHEN I CONNECT MY MAC USB EXTERNAL KEYBOARD TO THE POWERBOOK. The only way I can type using lower case letters is by permanently having one finger on the caps lock key, which isn't very convenient. I DON'T THINK THE PROBLEM IS TO DO WITH THE KEYBOARD ITSELF - I.E. PHYSICAL DAMAGE, OTHERWISE, WHY SHOULD IT BE POSSIBLE TO GET THE CAPS LOCK TO REMAIN OFF ONLY WHEN THE NUM LOCK IS DEPRESSED? PLEASE HELP ME SOLVE THIS PROBLEM. CAN I FOR EXAMPLE, REINSTALL AN UPDATE? I'M CURRENTLY DOWNLOADING THE 10.5.7 DMG UPDATE BUT WILL I BE ABLE TO RUN IT, IF I HAVE ALREADY UPDATED MY OS? WILL DOING THIS SOLVE MY PROBLEM? IF NOT PLEASE TELL ME WHAT WILL?

I noticed that some problems don't seem to get attention. I am typing this using a bluetooth keyboard on top of my G4 PowerBook, which is hardly an elegant solution to my caps lock problem. If I spend close to $2000 on a laptop, which is close to the most I spend on any consumer product after a house and car, is it unreasonable to expect that after a mere four years, it can be repaired, rather than simply tossed aside. I am an expat living in a SE Asian country without any Apple Authorised resellers etc. When I make the trip to Thailand to get my machine fixed, I'd like to know that someone there will know what to do to sort this problem, without me being faced with the prospect of having to pay a lot of money to buy a new one or replace hardware that is not in fact needing replaced. That is why I posted on this forum. Was I mistaken in thinking that in the entire Mac using community, there isn't more than one other person having the same issue as me? Is anybody from Apple aware of this problem and do they have any idea how to fix it? I'm not seeking to be antagonistic here, I'd just like to think that somebody, somewhere out there has some idea, what has gone wrong with my PowerBook and can help me get it fixed.
p.s I sorted out the large fuzzy Apple on startup by zapping the PROM, so that doesn't seem to be directly connected to the game of green light tennis I can now play between my caps lock and num lock keys. (My caps lock key is permanently lit and when I try to turn it off, it reduces the volume of my speakers and "types" "rfr" and other such gobbledegook.)

This just happened to my new (2 day old) Mini. Worked fine, but now it shows the caps light always lit. I CAN however toggle the caps lock on and off, just the light is always lit.

Do you think there are people here with the answer but are just holding out?

Why don't you try the obvious diagnostic tools... try booting into another User Account. Try booting with the install DVD. Try narrowing it down to hardware or software.

Re. "Do you think that there are people here with the answer who are just holding out?"
I don't know.
But guess what I took it to the nearest Authorized Apple Retailer, about 50 or so miles away, and because I did not buy my machine there, they refused to send it for repair. However, the sales assistant offered to do it for me privately, so I left my G4 with him, trusting him not to use my private data from fraudulent purposes, and to make sure that my Powerbook, made it to the service center in Bangkok and back again in one piece.
I now feel rather vulnerable to being ripped off, one way or another. Although it was just one key that was giving me a problem, I may need an entire new keyboard, but I can't say. I would like to have waited until I was next in Bangkok, but that could be several months, and I would like to have my Powerbook back and fixed before then.
Did I try all the things Gregory suggested? Yes. Sadly, in this instance going onto the forums, hasn't been much help, but it's been nice knowing that in the words of Michael Stipe: "You're not alone!" All the best to fellow "capslock misbehavior" syndrome sufferers. One day, we will unite and have nothing to lose but our slavery to the upper cases.
That is all.