I've been struggling with this for a few hours now.
I have included a newer version of Three20 in an iPad app, and can compile just fine with my debug build. Whenever I switch to another build, even a duplicate of debug, I get about 78 errors stating that UILabelAdditions.h could not be found.
It is in the Three20/src/Three20 directory, and as mentioned everything works fine with the debug build.
I've cleared cache, deleted the build directories, etc.
Any ideas?
It sounds like you have different header include directories listed for the two build directories.
In XCode, right click on your project, and choose Get Info. Under the Build tab, type in 'paths' in the search box to filter the properties below. Pay attention to the Header search paths. Now, switch your 'build configuration' between debug and release - are they the same? Add any to release that aren't in debug.
OK, so I finally gave up and reinstalled everything (it was happening on multiple apps). But if anyone ever has this problem and figures out a solution, I'd love to know about it (xCode, Geez).