Machine runs normally (OSX Panther)until I bring up Microsoft Word or Excel. Never gets Microsoft S/W loaded. Then, finally, display collapses in colorful lines or greys out. Necessary to restart. When I use the machine to do web operations, it goes on forever. When using iPhoto it may go for long periods, but will occasionally fold under this workload. Never fails in data transfers via airport as long as 10Gigbytes. Have replaced the motherboard myself with no improvement. I suspect the processor is having problems. Any suggestions?