try pure s3

app/uploaders/file_uploader.rb

@@ -8,7 +8,7 @@ class FileUploader < CarrierWave::Uploader::Base
        include CarrierWave::MiniMagick
   # Choose what kind of storage to use for this uploader
   if ENV['S3_KEY']
-    storage :fog
+    storage :s3
     
     def cache_dir
       "#{RAILS_ROOT}/tmp/uploads" if ENV['HEROKU'] == 'true'

config/initializers/s3.rb

@@ -1,9 +1,12 @@
 CarrierWave.configure do |config|
-  config.fog_credentials = {
-      :provider               => 'AWS',
-      :aws_access_key_id      => ENV['S3_KEY'],
-      :aws_secret_access_key  => ENV['S3_SECRET'],
-      :region                 => 'us-east-1'
-  }
-  config.fog_directory  = ENV['S3_BUCKET']
+  config.s3_access_key_id = ENV['S3_KEY']
+  config.s3_secret_access_key = ENV['S3_SECRET']
+  config.s3_bucket = ENV['S3_BUCKET']
+  #config.fog_credentials = {
+  #    :provider               => 'AWS',
+  #    :aws_access_key_id      => ENV['S3_KEY'],
+  #    :aws_secret_access_key  => ENV['S3_SECRET'],
+  #    :region                 => 'us-east-1'
+  #}
+  #config.fog_directory  = ENV['S3_BUCKET']
 end