As always, there are a few key issues to note regarding these updates. Pro Tools 11.1 is supported on the new Apple OS 10.9 (Mavericks) as well as OS 10.8.5 (Mountain Lion). However, Pro Tools 10.3.8 is only supported on 10.8.5 (Mountain Lion)- NO Support for 10.9 (Mavericks). If you are running PT11 and PT10 as a co-install, make sure you remain on 10.8.5 in order to have full compatibility.
If any of you are also running Avid Media Composer you will be please to know that you can now co-install Pro Tools 11.1 along with Media Composer.