Problems with early 09 iMacs?

[pilotkid]

Hey everyone thanks for tuning in! I'm on my second iMac, its a early 09 2.93ghz with 6gb of ram. The first iMac I had was purchased last June or July and I had it all the way tell November. During that time I had problems with the computer freezing at start up. To be more precise it would freeze right when you turn it on and the beach ball like thing is spinning, its like a greyish color. I took it to Apple a total of 6 times and they replaced the hard drive twice and the other times they would hook up their external hard drive and it would magically work. All of those problems were fixed by a brand new iMac the same specs as I had. Three months later my replacement iMac is doing THE EXACT same thing. Any thoughts on this? I swear it cant be user error. I do basic internet surfing, email, iTunes, and photo editing via Aperture 2 and 3. That is all my iMac is used for. Its turned off every night and turned on every morning. I cant think of anything that I could be doing to have this happen.
Oh also. Back when I was having problems with my first iMac Apple suggested that it might be my external time machine back up was corrupt. When I got my new iMac I manuall restored just my music and photos and then the external hard drive was reformatted and then reused as my current time machine back up.

Thanks for your time and thoughts
-Pilotkid

 

[PurrBall]

My 2.93 GHz iMac has had no problems and was purchased a year ago tomorrow.

 

[Hellhammer]

No problems with my 2.93GHz which is almost a year old

 

[definitive]

never had such problem on my system - not on leopard and not on snow leopard.

the only problem i'm having is constant image persistence on my screen. after booting it up, i get all kinds of lines and other artifacts on my screen no matter what.