The only support Adobe provides for CS5 is here in the forums.
CS5 is not supported on Yosemite or Mavericks. It works for some people but not others. You'll be on your own.
Make sure you haven't tried to copy or migrate it from your old computer. That definitely will not work. If you've done this, use the Adobe Cleaner Tool to clean up the mess:
You download a clean copy here: