An old problem reappeared with Ubuntu Natty Narwhal 64bit and Lotus Notes. And the fix is the same as for Lotus Notes 8.5.1 in Lucid Lynx. This must be done in order to have buttons and scroll lists:
sudo mv *.so.0 /opt/ibm/lotus/notes
Even with these libraries Lotus Notes does not look that good, scrollbars etc are blocky and the native theme is not used. But the most important is to get it running.