invalid gem format

[Brian Scott]

I'm having some issues installing gems such as Thin. Please see debug
below:

XXXXX@laptop:~$ sudo gem install sup --debug -V
Exception `NameError' at
/usr/lib/ruby/1.8/rubygems/command_manager.rb:161 - uninitialized
constant Gem::Commands::InstallCommand
Exception `Gem::LoadError' at /usr/lib/ruby/1.8/rubygems.rb:827 - Could
not find RubyGem test-unit (>= 0)

Exception `Gem::LoadError' at /usr/lib/ruby/1.8/rubygems.rb:827 - Could
not find RubyGem sources (> 0.0.1)

GET 200 OK: http://gems.rubyforge.org/latest_specs.4.8.gz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/sup-0.9.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/ferret-0.11.6.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/ncurses-0.9.1.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/rmail-1.0.0.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/highline-1.5.1.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/trollop-1.15.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/lockfile-1.4.3.gemspec.rz
GET 200 OK: http://gems.rubyforge.org/specs.4.8.gz
Exception `EOFError' at /usr/lib/ruby/1.8/net/protocol.rb:135 - end of
file reached
Exception `EOFError' at /usr/lib/ruby/1.8/net/protocol.rb:120 - end of
file reached
connection reset after 10 requests, retrying
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/mime-types-1.15.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/mime-types-1.16.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/gettext-2.1.0.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/fastthread-1.0.7.gemspec.rz
GET 200 OK:
http://gems.rubyforge.org/quick/Marshal.4.8/locale-2.0.5.gemspec.rz
Installing gem ferret-0.11.6
Exception `Gem:ackage::FormatError' at
/usr/lib/ruby/1.8/rubygems/package/tar_input.rb:110 - No metadata found!
Exception `Gem::InstallError' at
/usr/lib/ruby/1.8/rubygems/installer.rb:121 - invalid gem format for
/var/lib/gems/1.8/cache/ferret-0.11.6.gem
ERROR: Error installing sup:
invalid gem format for /var/lib/gems/1.8/cache/ferret-0.11.6.gem