We have InDesign as part of our CS5 package. We have just installed CS5 on to a new Mac with Yosemite. The applications generally work fine but I cannot update the software despite numerous attempts. It goes through the whole downloading process until nearly the end when I get a message saying the download failed and to try again.
CS5 is unsupported under Yosemite. That said, have you tried downloading the updates manually and installing them?