For those intersted here is the fix:
http://forums.macrumors.com/showthread.php?t=392190
It did work!!! I was highly impressed
For iMacs with the ATI Radeon HD 2600 you need to go into the main application folder, then "SimCity 4 Data" folder :
1. Open "Video Cards.sgr" with TextEdit
2. Locate the end of the list of "vendor "ATI" 0x1002"
3. Add this line to the end, but before the word "end" :
card 0x9583 "Radeon HD2600"
4. Save and close.
5. Open "Graphic Rules.sgr"
6. Locate the ATI rules, near the bottom like so:
stringMatch cardIdentity "*7?00*"
stringMatch cardIdentity "*8?00*"
stringMatch cardIdentity "*9000*"
stringMatch cardIdentity "*9100*"
stringMatch cardIdentity "*9200*"
stringMatch cardIdentity "*9300*"
stringMatch cardIdentity "*9400*"
stringMatch cardIdentity "ATI, Radeon"
stringMatch cardIdentity "ATI, Radeon VE"
stringMatch cardIdentity "ATI, Radeon Mobility"
stringMatch cardIdentity "ATI, Radeon FireGL"
7. You will add just one line:
stringMatch cardIdentity "ATI, Radeon HD2600"
8. It should look like this:
stringMatch cardIdentity "*7?00*"
stringMatch cardIdentity "*8?00*"
stringMatch cardIdentity "*9000*"
stringMatch cardIdentity "*9100*"
stringMatch cardIdentity "*9200*"
stringMatch cardIdentity "*9300*"
stringMatch cardIdentity "*9400*"
stringMatch cardIdentity "ATI, Radeon HD2600"
stringMatch cardIdentity "ATI, Radeon"
stringMatch cardIdentity "ATI, Radeon VE"
stringMatch cardIdentity "ATI, Radeon Mobility"
stringMatch cardIdentity "ATI, Radeon FireGL"
9. Save and close.