I have sort of the same problem.
It started when the Imac went to sleep (with "put hard disk to sleep when possible" checked as a "energy saver" preference option") and I tried to wake it up... I would get the beach ball, and had to shut down using the power button.
For a while it would start right up again.
Now I get the flashing question mark when I try to start up.
So I was pulling the power plug, and waiting over 15 minutes before starting up with a pram zap, and then it would start.
But that also stopped working yesterday.
Now if I pull the plug and wait a few hours (sometimes overnight) and start up with a pram zap, it will usually start up.
I have turned off the "put hard drive to sleep when possible" option in Energy Saver preferences and it has been running for a few hours now.
I haven't shut down yet to see if it will restart, because I don't want to be without my computer till the new one gets here, and then I will decide if I should spend the money on a hard drive to see if that gets this IMac going - still a good machine, but now worth hundreds in repairs.
I had also reinitialized the drive and reinstalled the system software. That made no difference. Wiped it with the 7 times erase option - took 11 hours.
So, I am thinking it's a drive, but will probably try the memory trick also.
Glad to share
Did you change something to cause this to happen or did it start acting up for no apparent reason?
door Scott Head
Are you holding down the "C" key when trying to boot from the optical drive?
@Nat, i have not change anything befor the problem occured. I tried to replaced the HDD and boot from optical drive, upon insertion of the installation CD it spins, after several seconds it displays the FLASHING FOLDER AND QUESTION MARK...
door Cled Tayamen
@mayer, yes i do pressing "C" upon booting system installation CD but still FLASHING FOLDER AND QUESTION MARK displayed...
door Cled Tayamen