Good to hear CS5 was working with Mavericks.
Something changed, so I'd think again... lol.
Also, any Mavericks updates or the like?
Changes in any of your data disks?
I would try recreating preferences and making sure you are running as administrator (even if you did not need to before).
http://helpx.adobe.com/x-productkb/global/troubleshoot-system-errors-f reezes-mac.html