Great idea, great instructions, did not work on my iMac. The computer came back up and was unable to find the router address. However, I found that running "network diagnostics" fixes the problem without having to reboot the router. This is not a fix, but a work-around. Apple will have to address the real issue.

Using a cable would be impractical since I have my router downstairs and my desktop upstairs. The problem is eliminated if I never allow the iMac hard drive to sleep, but this is hardly a fix. Apple will apparently how to address the issue.