It seems that Karmic Koala, the last version of Ubuntu, has dropped support for versions of GCC/G++ prior to version 4.1.
Here is a quick script to add GCC and G++ 3.4 from the repository of the previous version:
mkdir DELEME &&
cd DELEME &&
wget http://ge.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.4/libstdc++6-dev_3.4.6-6ubuntu3_i386.deb &&
wget http://ge.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.4/cpp-3.4_3.4.6-8ubuntu2_i386.deb &&
wget http://ge.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.4/gcc-3.4_3.4.6-8ubuntu2_i386.deb &&
wget http://ge.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.4/gcc-3.4-base_3.4.6-8ubuntu2_i386.deb &&
wget http://ge.archive.ubuntu.com/ubuntu/pool/universe/g/gcc-3.4/g++-3.4_3.4.6-6ubuntu3_i386.deb &&
sudo dpkg -i *.deb &&
cd .. &&
rm -rf DELEME
