iMac Mid 2007 20 inch OS upgrade problems
With the upcoming shut down of MobileMe, I am in the process of migrating my intel mac to OS X 10.7
My Mid-2007 20 inch iMac is supposedly able to run Lion. It has 4 GB of RAM. It has been running Leopard 10.5.8 without problems thus far. I did a clean install of Snow Leopard and then an in-place upgrade of Lion. Since then the machine is unusable. The machine boots and goes into a blank screen and sometimes will load the desktop. When it does load the desktop, it will freeze with a spinning beach ball and no response for hours (I've left it on all day to see if the system will respond). Graphics corruption and glitches are noticeable just prior to the freezes.
I then wiped the HD clean and installed Snow Leopard. To my surprise similar problems were found. I ran the AHT and did the extended testing and no problems were found. Memory checks were good and no problems with the graphics card were reported.
I've done the usual PRAM / PMU reset and this does not help. I've googled and searched the web and found some people that had similar problems but not exactly the same.
As a last resort, I am posting this message to see if anyone in this forum has any helpful information or suggestions.
Thanks in advance.
RB