I'm back from a wonderful (but way too short) trip to NH and the machine booted just fine again (no mysterious message about my memory cache and contacting an Apple Technician.) I still don't feel too confident about it though. I will try some of your suggestions and run the memory test tonight. I will also try disabling the built in memory test if the message comes back. But since it doesn't recognize my L2 cache when it happens, I think something will have to be replaced if it becomes an ongoing situation. Thanks so much for your help! Lynn .......I think I've got big problems. This morning when trying to reboot my computer after a crash, my boyfriend discovered this message on boot. "Apple's built-in memory test has discovered a problem with memory cache. Please contact an Apple Service Technician." It then proceeds to boot, I get my desktop, but then I get the message that the finder has unexpectedly quit and I should restart. .........