Afaik, g++ 4.x is unstable with BMax and may or may not work. If it's not working then you should just manually download the deb packages for i386 listed as red on this page:
http://packages.debian.org/stable/devel/g++-3.3
Not sure about the 64-bit question.
http://packages.debian.org/stable/devel/g++-3.3
Not sure about the 64-bit question.