I was unable to demonstrate my Xcode projects today at my ADHOC presentation. They produced an obscure error when building.
Why?
Not because I’d moved the project, or renamed the project or its enclosing folder. Xcode can handle that.
It was because I’d renamed the enclosing folder to contain a comma.
I remember when Project Builder location paths couldn’t contain a space.
This is probably a similar issue having to do with the underlying, Unix-based technologies (i.e. gcc).
I wonder if the fix will involve merely putting in a few more quotes around command-line options, or if it would require deeper surgery.
Weaponized Fluff 
I think it’s actually a problem with Xcode. All paths are separated by spaces in a makefile (they use the C-style or rather shell-style escaping). It would work in Project Builder if you put quotes around the space-containing folders. However, people complained (even I hated it), and so they made it comma-delimited.
I’m guessing that now it’s Xcode splitting the paths at that point. Unfortunately, it’s not as easy as editing a makefile to get Xcode to work with paths that may need escaping.
Of course, this is just speculation.