When I create a new OS X \"Game\" project with Sprite Kit, and set a breakpoint anywhere I can see the variable values just fine:
In my case this was happening because of redundant import statements in my project.
My project mixes swift and objc files, so I have import statements in the bridging_header.h file.
In my bridging_header.h I had #import blah.h
In one of the swift files, I was importing a redundant header from a framework
@import blah // From blah.framework
I removed the redundant import from the swift file, that seems to have fixed it.