today i had the problem under Ubuntu 11.10 64bit, that adb from the Android SDK failed to start with the output
error while loading shared libraries: libncurses.so.5: wrong ELF class: ELFCLASS64
The solution is quite simple: The system has a 64bit environment, but the package from google is 32bit. So you have to install the 32bit libraries via
sudo apt-get install ia32-libs