This is what you should see as a result of your plugin install:
/widgets 516 > script/plugin install git://github.com/paolodona/rails-widgets.git
Initialized empty Git repository in /Users/rick/widgets/vendor/plugins/
remote: Counting objects: 78, done.
remote: Compressing objects: 100% (71/71), done.
remote: Total 78 (delta 8), reused 21 (delta 0)
Unpacking objects: 100% (78/78), done.
* branch HEAD -> FETCH_HEAD
Did you omit this output from your mail message or what? Was any
output produced when you ran the install?