I've been installing Ubuntu 11.04 at last. Unfortunately, rvm choked up. It claimed to install properly, but choked when trying to do the simplest gem commands.
ERROR: Loading command: install (LoadError) no such file to load -- zlib ERROR: While executing gem ... (NameError) uninitialized constant Gem::Commands::InstallCommand
The solution was hidden in some comments in stack overflow.
rvm pkg install zlib rvm uninstall 1.8.7 #this can be 1.9.2 or ree, whatever rvm install 1.8.7 --with-zlib-dir=$rvm_path/usr