My imac started having issues shortly after running the lastest software update for Mountain Lion. The issues are applications freezing and then trouble at shut down even after force closing the affected applications. A friend took a look at the computer and suggested trying to reinstall software from my install disc to see if that might remedy the issue. I was unable to do the reinstall due to the computer telling me it could not open the disk and showing a yellow exclamation point on my drive. I have run disk repair and the short hardware test using the install discs and haven't turned up any issues. Any suggestions? My warranty is expired and I did not purchase the extended care Computer is about 18months old:
Processor 3.2 GHz Intel Core i3
Memory 4 GB 1333 MHz DDR3
Graphics ATI Radeon HD 5670 512 MB
Software OS X 10.8.2 (12C54)