Can't run "gem list"!

I get an error when i run:

vagrant@vagrantup:~$ sudo gem list
ERROR:  Loading command: list (LoadError)
    no such file to load -- zlib
ERROR:  While executing gem ... (NameError)
    uninitialized constant Gem::Commands::ListCommand

Even if I don't use sudo I get the same error message.

It's on Ubuntu 10.4 and I have installed zlib libraries:

vagrant@vagrantup:~$ sudo aptitude search zlib
p   gambas2-gb-compress-bzlib2                                                    - The Gambas bzlib2 component                                                             
p   gambas2-gb-compress-zlib                                                      - The Gambas zlib compression component                                                   
p   haskell-zlib-doc                                                              - Compression and decompression in the gzip and zlib formats; documentation               
p   libcompress-raw-zlib-perl                                                     - low-level interface to zlib compression library                                         
p   libcompress-zlib-perl                                                         - Transitional dummy package for Compress::Zlib                                           
i   libghc6-zlib-dev                                                              - Compression and decompression in the gzip and zlib formats                              
v   libghc6-zlib-dev-0.5.2.0-d3bd7                                                -                                                                                         
v   libghc6-zlib-doc                         开发者_运维技巧                                     -                                                                                         
p   libghc6-zlib-prof                                                             - Compression and decompression in the gzip and zlib formats; profiling libraries         
v   libghc6-zlib-prof-0.5.2.0-d3bd7                                               -                                                                                         
p   libio-compress-zlib-perl                                                      - Transitional dummy package for IO::Compress::Zlib                                       
p   libio-zlib-perl                                                               - IO:: style interface to gzip/zlib compressed files/handles                              
p   libjzlib-java                                                                 - reimplementation of zlib in pure Java                                                   
i   libzlib-ruby                                                                  - transitional dummy package                                                              
v   libzlib-ruby1.8                                                               -                                                                                         
p   zlib-bin                                                                      - compression library - sample programs                                                   
i   zlib1g                                                                        - compression library - runtime                                                           
p   zlib1g-dbg                                                                    - compression library - development                                                       
i   zlib1g-dev                                                                    - compression library - development                                                       
i   zlibc                                                                         - An on-fly auto-uncompressing C library

Im using http://www.vagrantup.com and the error comes after i have installed rvm.

What could the problem be?

How was Ruby installed? If Ruby was installed without zlib support, that would be the problem.

You can read my article here on installing RVM on Ubuntu. You must have both zlib and the zlib-dev packages installed before compiling Ruby (along with some other packages from Ubuntu). You'll probably just need to install these and re-compile Ruby.