I updated to 10.10.3 today with no problems. However, there is now an Xcode update (6.3) in the App Store, but it won't install. I go to the Updates tab and click on the Update button, but it just goes grey and doesn't show the download progress bar. No other updates are available yet so I don't know whether this is unique to Xcode or a bigger problem with my installation of 10.10.3. I've rebooted, but have not yet tried reapplying the combo update. Has anyone else run into this?