iMac 27" with OSX Lion

[JerseyArtist]

I have a two month old iMac 27" screen which came with Lion installed. Everything OK for first month, now every time I stop using the computer for a short time, everything freezes. I have to hold start up button to turn Mac off and reboot.
I have called Apple and spent 2 hours discussing the problem and every answer they gave me worked for an hour and then I was back to square one with the problem.

 

[chscag]

It's probably time to make an appointment with your local genius bar and take it on in. It's a large heavy machine to carry but it's best to let them diagnose it in person rather than over the phone.

 

[JerseyArtist]

That was the answer I was afraid I was going to receive. If this was the first Mac I ever bought I would never buy another.
I had a small trouble with the wireless mouse and Apple replaced it with a refurbished one that doesn't work. I decided to keep my brand new one. Bad business practice.
Thanks for your help.