I've run into a seemingly impenetrable compile error related to Boost, which I've reduced to including a single boost header file. In compiling (with GCC 4.2 on Mac OS X 10.6.8) an empty file containing only this include:

#include "boost/date_time/posix_time/posix_time.hpp"

...generates these errors:

 In file included from ../../../Boost Libraries/Boost_1_55_0/boost/type_traits/has_left_shift.hpp:43,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/lexical_cast.hpp:165,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/string_parse_tree.hpp:13,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/period_parser.hpp:14,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/date_facet.hpp:23,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/gregorian/gregorian_io.hpp:16,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/gregorian/gregorian.hpp:31,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_formatters.hpp:12,
                 from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/posix_time.hpp:24,
                 from /Users/homedir/dev/TheProject/Mac/Xcode/../Source/feature/test.cpp:12:../../../Boost Libraries/Boost_1_55_0/boost/type_traits/detail/has_binary_operator.hpp:155: error: expected unqualified-id before 'do'In file included from ../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/posix_time.hpp:34,
                 from /Users/homedir/dev/TheProject/Mac/Xcode/../Source/feature/test.cpp:12:../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_parsers.hpp:40: error: expected `}' at end of input
../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_parsers.hpp:40: error: expected unqualified-id at end of input
../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_parsers.hpp:40: error: expected `}' at end of input
../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_parsers.hpp:40: error: expected `}' at end of input
../../../Boost Libraries/Boost_1_55_0/boost/date_time/posix_time/time_parsers.hpp:40: error: expected `}' at end of input

These Boost libraries are being used as "headers only" -- unbuilt.

Xcode is generating: /Developer/usr/bin/gcc-4.2 –x c++  (plus all the other options, paths, etc)