Threading support detection is broken if you combine boost-1.48 with gcc-4.7. See $URL for more info. Boost actually compiles and installs fine, but applications that need it do not find the threading support. This is fixed in boost-1.49. Your call if you want to backport the simple upstream patch. (Found this while trying to build hugin, you end up with errors like: [0mcd /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0_build/src/hugin_base && /usr/bin/x86_64-pc-linux-gnu-g++ -Dhuginbase_EXPORTS -DHUGIN_HSI -DNDEBUG -march=native -O2 -pipe -ggdb -fPIC -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0_build/src -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/foreign -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/foreign/vigra -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/celeste -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0_build/src/celeste -I/var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src -I/usr/include/OpenEXR -I/usr/include/boost-1_48 -I/usr/include/python2.7 -o CMakeFiles/huginbase.dir/algorithms/basic/StraightenPanorama.cpp.o -c /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base/algorithms/basic/StraightenPanorama.cpp In file included from /usr/include/boost-1_48/boost/thread/detail/platform.hpp:17:0, from /usr/include/boost-1_48/boost/thread/thread.hpp:12, from /usr/include/boost-1_48/boost/thread.hpp:13, from /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base/vigra_ext/MultiThreadOperations.h:31, from /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base/vigra_ext/ImageTransforms.h:42, from /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base/nona/Stitcher.h:49, from /var/tmp/portage/media-gfx/hugin-2011.4.0/work/hugin-2011.4.0/src/hugin_base/algorithms/nona/NonaFileStitcher.cpp:33: /usr/include/boost-1_48/boost/config/requires_threads.hpp:29:4: error: #error "Threading support unavaliable: it has been explicitly disabled with BOOST_DISABLE_THREADS" )
https://bugs.gentoo.org/show_bug.cgi?id=407761#c3 says the fix from boost-1.49 wont be backported to boost-1.48, because gcc-4.7 is still p.masked. Dublicate of bug 407761? The same boost ticket is also linked from that bug.
Indeed - this looks like a duplicate of Bug 407761.
*** This bug has been marked as a duplicate of bug 407761 ***