CS3 is definitely not supported under Yosemite (Mac OS X 10.10).
There are only two upgrade options:
1) Purchase a perpetual license to InDesign CS6. This version is supported under Yosemite, but it's three years old already, and there is no guarantee that it will survive the next Apple upgrade.
2) Get a subscription to InDesign CC. This will receive regular updates and will always run on current operating systems.
Thanks Steve. That's what I suspected. I appreciate your help!
I upgraded my mac system to 10.10.2. CS3 works perfectly well in all other ways with the new system. Do I need to upgrade CS3?
Was it an in place upgrade or clean install. Have you tried reinstalling CS3?
I didn't have my original CS3 to try an re-install so I just went ahead and am trying out CC. So far so good. No problems working with my old files. Thanks for your response!