fatal: bad revision 'HEAD'

Hello,

I am having trouble installing Ruby on Rails plugins from github.   
when I run e.g. script/install plugin git://github.com/thoughtbot/ 
paperclip.git I get:

 > Initialized empty Git repository in /path/to/my/project/vendor/ 
plugins/paperclip/.git/
 > fatal: bad revision 'HEAD'
 > refusing to pull with rebase: your working tree is not up-to-date

I don't have any problems with git in general, but this error happens  
every time I try to install from github - even when it's a brand new  
rails app.

the github support team tells me it looks like a git issue - any  
suggestions would be appreciated!

thanks,
Joel