FC-5 question about gcc, g++

[Peter Horst]

I'm trying to compile nmap on a FC-5 system, latest kernel, gcc version:

Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
--infodir=/usr/share/info --enable-shared --enable-threads=posix 
--enable-checking=release --with-system-zlib --enable-__cxa_atexit 
--disable-libunwind-exceptions --enable-libgcj-multifile 
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada 
--enable-java-awt=gtk --disable-dssi 
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre 
--with-cpu=generic --host=i386-redhat-linux
Thread model: posix
gcc version 4.1.1 20060525 (Red Hat 4.1.1-1)

The nmap configure script fails, saying that I don't have a c++ 
compiler.  If I use ./configure CXX=/usr/bin/gcc it'll get part of the 
way through then choke at:

checking whether we are using the GNU C++ compiler... no
checking whether /usr/bin/gcc accepts -g... no
checking dependency style of /usr/bin/gcc... none
checking how to run the C++ preprocessor... /lib/cpp
configure: error: C++ preprocessor "/lib/cpp" fails sanity check

What am I missing?  Thanks much.