(Update: 2010/08/25) Rescatux 0.08 won’t fix EXT4 based systems. That means that it will only work with Ubuntu 8.04 and upgrades to Ubuntu 8.10 (not Ubuntu 9.04, Ubuntu 9.10…). I hope that I had known this before but Ubuntu users did not reply to my Rescatux test request on ubuntuforums.org forum.
You can try 0.10 only if your system is AMD64. I suppose it will handle ext4 without any problem.