I included this header into one of my own: http://codepad.org/lgJ6KM6b
When I compiled I started getting errors like this:

CMakeFiles/bin.dir/SoundProjection.cc.o: In function `Gnuplot::reset_plot()':
/usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/new:105: multiple definition of `Gnuplot::reset_plot()'
CMakeFiles/bin.dir/main.cc.o:project/gnuplot-cpp/gnuplot_i.hpp:962: first defined here
CMakeFiles/bin.dir/SoundProjection.cc.o: In function `Gnuplot::set_smooth(std::basic_string, std::allocator > const&)':
project/gnuplot-cpp/gnuplot_i.hpp:1041: multiple definition of `Gnuplot::set_smooth(std::basic_string, std::allocator > const&)'
CMakeFiles/bin.dir/main.cc.o:project/gnuplot-cpp/gnuplot_i.hpp:1041: first defined here
CMakeFiles/bin.dir/SoundProjection.cc.o:/usr/include/eigen2/Eigen/src/Core/arch/SSE/PacketMath.h:41: multiple definition of `Gnuplot::m_sGNUPlotFileName'

I know it's hard to see in this mess, but look at where the redefinitions are taking place. They take place in files like /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/new:105. How is the new operator getting information about a gnuplot header? I can't even edit that file. How could that ever even be possible? I'm not even sure how to start debugging this. I hope I've provided enough information. I wasn't able to reproduce this in a small project. I mostly just looking for tips on how to find out why this is happening, and how to track it down.

Thanks.