Letters are repeated when I am writing

I've replaced the keyboard once, but it's
just as bad as the first one

Thanks,
Onno

How many different keyboards would have to be tried to convince you that it wasn't the keyboard that was the cause of the problem? The fact that your iMac contained a major preference setting for the key repeat should have alerted you that it wasn't a hardware issue.

explain why the evidence I've provided does not prove
that the problem is with the keyboards.

You have provided no evidence whatsoever. The only evidence that the keyboard itself was faulty would be if it were used in place of a known to be accurate keyboard and at that time continued its faulty behavior. Now that would be a "bad" keyboard, and I'm sure that Apple would throw it in the trash just as fast as you seem to be inclined to do.

Why should I completely erase my hard-drive and reinstall all software

You shouldn't. You should reset the PRAM, as was suggested.

attempt to fix what would seem to be a simple (and common) problem?

You've got part of that right, as it IS a simple problem, but not so common that you didn't have to dig up a 5-month old thread to which you could post!

Hi, I would Repare permissions and then Turn Off Computer,Before restarting unplug all USB and FW cables. Reconnect keyboard into a different USB socket then previously. then plug mouse into USB socket on the computer. Then restart and reset keyboard/ mouse settings and then check it. You should be good to go.

... L

17"C2D S/Drive-VideoiPod-IBook14" (max ram)-3 Nanos-iSight Camera Mac OS X (10.4.8) 2 LaCie160gb Ext HDs-Prostar Laptop with XP-Leica,Olympus,KM-Digital Cameras

"the problem still occurs"

Have you checked the Universal Access panel of System
Preferences?

Have you performed disk repair?

If none of those help, and the PRAM reset does not
help, I would erase the hard drive, write zeroes to
it, and then reinstall the OS. If it still happened
then, you'd be in a position to have Apple repair or
replace the computer. Otherwise, you'll be like the
others, sitting around and complaining. Your choice:)

This is just BAD advice and I hope it doesn't lead anyone to follow it!
My solution of replacing the keyboard with a macally was far less painful and gave immediate results (for me). Hardly "sitting around and complaining"! The purpose of taking any action is to get results. I did and I did! Not everyone may have the exact same problem but a blanket solution for anyone with the same symptoms, of erasing the hard drive isn't exactly helpful.

Nothing but a cheap shot, but from your posts, that's something you're quite familiar with.

Did you EVER try using your "faulty" Apple USB keyboard with your iMac since? Have you tried to use it with another Mac?

If not, then you're the one giving REALLY BAD advice, since the likelihood that there is anything at ALL wrong with your keyboard, or the keyboards of ANY of the other posters to this thread, is close to nil.

You should re-read the terms of use, over to the right. If you receive ANY benefit from advising the purchase of unnecessary keyboards, those posts are not allowed.