The camera (Powershot S5 IS) suddenly quit working. It will not power on (tried two sets of fresh batteries). Am I overlooking something very simple? Is it related to the small button battery that protects the memory?

Things to check first for a camera that won't turn on are battery contact points, and micro switches that are located on the battery and memory card doors. Troubleshooting tips on other things that need to be checked may be seen here. These tips won't work for every case, but they're worth a try.