failed updated, tried to roll back but cannot get site to start

I tried to update a rails site going from 2.3.5 to 2.3.15, which failed.
I had a backup of the site which I restored, but the site still will not
start. It errors with:

undefined method `name' for "actionmailer":String

0 /usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb
268 in ==' 1 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb 217
in===' 2 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb 217 in
matching_specs' 3 /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb
36 infind_all' 4 /usr/lib/ruby/site_ruby/1.8/rubygems/specification.rb
412 in each' 5 /usr/lib/ruby/site_ruby/1.8/rubygems/specification.rb 411
ineach' 6 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb 216 in
find_all' 7 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb 216
inmatching_specs' 8 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb
238 in to_specs' 9 /usr/lib/ruby/site_ruby/1.8/rubygems/dependency.rb
256 into_spec' 10 /usr/lib/ruby/site_ruby/1.8/rubygems.rb 1231 in gem'
11 /usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/rails/gem_dependency.rb
73 inadd_load_paths' 12
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb 301 in
add_gem_load_paths' 13
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb 301 ineach'
14 /usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb 301 in
add_gem_load_paths' 15
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb 132
inprocess' 16 /usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb
113 in send' 17
/usr/lib/ruby/gems/1.8/gems/rails-2.3.5/lib/initializer.rb 113 inrun' 18
/var/www/lloyds/config/environment.rb 9
19 /usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb 55 in
gem_original_require' 20
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb 55 inrequire'

My gem list

* LOCAL GEMS *

actionmailer (2.3.5, 2.3.2)
actionpack (2.3.5, 2.3.2)
activerecord (2.3.5, 2.3.2)
activeresource (2.3.5, 2.3.2)
activesupport (2.3.5, 2.3.2)
authlogic (2.1.3)
exception_notification (1.0.20090728)
fastthread (1.0.7)
mysql (2.8.1)
paperclip (2.3.1.1)
passenger (2.2.9)
rack (1.1.6, 1.0.1)
rails (2.3.5, 2.3.2)
rake (0.8.7)
rubygems-update (1.8.25)
rubyzip (0.9.1)

The older versions of 2.3.x get very cranky indeed with modern versions of Rubygems. Try rolling back to something of a more appropriate vintage (I’ve got an old 2.3 app that uses rubygems-update 1.4.2 successfully).

–Matt Jones