std::string missing from gcc 4.0?

[Adrian <adrian dot down at gmail dot com>]

Hello,

I am trying to use the gcc version 4.0.1 that came installed on my
PowerBook G4, powerpc-darwin machine to install some software from
source code (the software is the ROOT data analysis program, from
www.root.cern.ch).  When I try to run the "make" command in the
directory created by downloading the ROOT software via cvs, I receive
an error because it appears that there is a problem with the "string"
header file.  The code I am trying to compile thinks string is part of
the std, and gcc seems to disagree.  Some output from this error is
printed at the end of this message.

I'm sorry if this is a novice question.  I only interact with gcc to
the extent that it is necessary for me to install applications for
research.  I have asked some of my colleagues about this problem, but
none of them experienced it when installing the ROOT software.  Please
let me know if there is any information that would be useful in
diagnosing this problem.

Thank you very much,
Adrian Down