Rubygems undefined method 'loaded_from=' for nil::NilClass

...here is the stack:

# gem list --backtrace

*** LOCAL GEMS ***

ERROR: While executing gem ... (NoMethodError)
undefined method 'loaded_from=' for nil::NilClass
/usr/lib/ruby/site_ruby/1.8/rubygems/cache.rb:32:in `from_installed_gems'
/usr/lib/ruby/site_ruby/1.8/rubygems/cache.rb:29:in `each'
/usr/lib/ruby/site_ruby/1.8/rubygems/cache.rb:29:in `from_installed_gems'
/usr/lib/ruby/site_ruby/1.8/rubygems/cache.rb:28:in `each'
/usr/lib/ruby/site_ruby/1.8/rubygems/cache.rb:28:in `from_installed_gems'
/usr/lib/ruby/site_ruby/1.8/rubygems.rb:97:in `cache'
/usr/lib/ruby/site_ruby/1.8/rubygems/gem_commands.rb:354:in `execute'
/usr/lib/ruby/site_ruby/1.8/rubygems/gem_commands.rb:443:in `execute'
/usr/lib/ruby/site_ruby/1.8/rubygems/command.rb:49:in `invoke'
/usr/lib/ruby/site_ruby/1.8/rubygems/cmd_manager.rb:82:in `process_args'
/usr/lib/ruby/site_ruby/1.8/rubygems/cmd_manager.rb:55:in `run'
/usr/lib/ruby/site_ruby/1.8/rubygems/gem_runner.rb:9:in `run'
/usr/bin/gem:6

-----Messaggio originale-----
Inviato: martedì 13 luglio 2004 18.44
nil::NilClass

Petrucci Fabio said:

You are right... the command was :

# gem install log4r-1.0.5.gem

Good. I was worried about a version mismatch.

now running this command:

# gem list --traceback gives...

ERROR: While executing gem ... (OptionParser::InvalidOption)
  invalid option: --traceback

Oops. That was my fault. I was working from memory instead of checking
the docs.

The option is --backtrace. Please try it again.

Sorry for the confusion.

···

Da: Jim Weirich [mailto:jim@weirichhouse.org]
A: ruby-talk ML
Oggetto: Re: R: rubygems undefined method 'loaded_from=' for

--
-- Jim Weirich jim@weirichhouse.org http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)