avenue33:
I wasn't able to replicate the workspace integrity error on my MacBook. Are there other time-consuming processes running? as Mac OS X is a multitasking OS, processes may conflict.What is your Mac? Try with only Xcode launched.
You could also try the procedure we've already discussed at Arduino on Xcode Project — Official Thread - #306 by avenue33 - Libraries - Arduino Forum
I logged out of my mac and back in again to make sure nothing else was running. I created a new project and got the same workspace integrity error.
I looked at the post you referenced, but I don't have an Xcode folder in my Documents folder. So I couldn't do the terminal commands.
I tried installing xcode rev 50 (still had it in my download folder) and created a new project and this worked fine, no errors.
My computer is a Mac Pro with Quad-core Intel Xeon, 8GB RAM.