[minniepott]

My iMac isn't waking up from sleep.
Not sure what to do about it.

[bastion]

What have you tried so far? If "not waking up" means one day you tried hitting keys and maybe clicking the mouse and it didn't respond, the next step is usually to unplug and then reconnect the mouse and/or keyboard and try again. Sometimes there's just this transient situation where the bus doesn't seem to recognize the devices.
If, on the other hand, this is a recurring issue there's probably more investigation to be done.

[albloom]

You might try my "solution." I only authorize display
sleep. No problems.

[nnager]

When my desktop G4 QuickSilver (2001) failed to wake this weekend, I eliminated a number of possible causes and then went into the machine to replace its PRAM battery with one I picked up at Radio Shack. That did the trick. So, after you go through the drills to rule out the easier and more likely suspects, consider the possibility of a weak battery.
Respectfully, Norm
Edited to add: Among other things I did before opening the computer case to replace the battery:
--Checked to make sure all my connections were well-seated
-- Shut down and did a restart by pressing and holding the power button and then pressed again to re-start the Mac.
-- When that didn't work, I did another restart and zapped P-RAM memory. (Immediately after pressing the G4 "on" button to boot/start computer, simultaneously press four keys--option, command/apple, p and r-- and hold all four down until hear computer bong four times. Then release.)

[minniepott]

Well,
I've done everything I can think of to get this baby to wake up, but so far all I can do is shut down and start up after it's been put to sleep. I have a cordless keyboard and mouse (I'm sure this makes a difference and I should have mentioned it before).
This has never been a problem before and the problem didn't start until I updated the system software (10.4.8).
I'm going to try display sleep only and see if there's still a problem
Thank You