First, you should know whether you follow the document below:
http://gabriel.github.com/gh-unit/docs/appledoc_include/guide_install_ios_4.html
and then you need to check the GHUnitIOS framework in the xcode, can't you see some ".h" files below the "headers" group? if not, may be the GHUnitIOS framework is not proper.go to location "/GHUnitIOS.framework/Versions/A/", and copy all the 3 files in it, go to the location "GHUnitIOS.framework/", paste them and then run the test project. is that ok?
if you can see those ".h" files in the framework, maybe the build settings is not properly set.
you should check the search path.