Errors on x86_64 (broken c++ headers?)

[Quentin Spencer <qspencer ieee org>]

I resubmitted octave to be built yesterday, with more odd results. 
Everything looks fine for PPC, but for i386, the build appears to have 
completed, but there is still a failure.log file that says "Build 
process terminated by timeout". For x86_64, the build failed. Looking at 
the log file, there are a whole lot of errors that look something like this:

g++ -c  -fPIC -I. -I../.. -I../../liboctave -I../../src 
-I../../libcruft/misc  -DHAVE_CONFIG_H  -Wall -W -Wshadow -Wcast-align 
-Wcast-qual -Wpointer-arith -Wwrite-strings -Weffc++ -g -O2 quit.cc -o 
pic/quit.o
In file included from quit.cc:30:
/usr/lib/gcc/x86_64-redhat-linux/4.0.0/../../../../include/c++/4.0.0/iostream:43:28: 
error: bits/c++config.h: No such file or directory
In file included from 
/usr/lib/gcc/x86_64-redhat-linux/4.0.0/../../../../include/c++/4.0.0/ios:43,
                from 
/usr/lib/gcc/x86_64-redhat-linux/4.0.0/../../../../include/c++/4.0.0/ostream:44,
                from 
/usr/lib/gcc/x86_64-redhat-linux/4.0.0/../../../../include/c++/4.0.0/iostream:44,
                from quit.cc:30:

So, the errors appear to be caused by the c++ header files. How is it 
possible that the header files are broken on one arch and not another? 
Any other insights into what might have caused this and how to fix it?

-Quentin