このエラーに関するアイデア - sass compilejust が失敗する - gem update --system と gem update を試し、sass gem を削除して再インストールしました
sudo sass --update --trace styles.scss overwrite styles.css
Password:
/Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/plugin/staleness_checker.rb:27: uninitialized constant Sass::Plugin::StalenessChecker::Mutex (NameError)
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `gem_original_require'
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `require'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/plugin/compiler.rb:7
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `gem_original_require'
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `require'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/plugin.rb:4
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `gem_original_require'
from /Library/Ruby/Site/1.8/rubygems/core_ext/kernel_require.rb:53:in `require'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/exec.rb:381:in `watch_or_update'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/exec.rb:326:in `process_result'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/exec.rb:41:in `parse'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/../lib/sass/../sass/exec.rb:21:in `parse!'
from /Library/Ruby/Gems/1.8/gems/sass-3.2.11/bin/sass:9
from /usr/bin/sass:23:in `load'
from /usr/bin/sass:23