Rails - Mar 2006 - mongrel gemplugin name error

Hi,

Deploying in production on a server (debian sarge + ruby1.8.4)
I got some problems:
 > mongrel_rails start -q
/usr/lib/ruby/gems/1.8/gems/mongrel-0.3.11/bin/mongrel_rails:6: 
uninitialized constant GemPlugin (NameError)
         from /usr/bin/mongrel_rails:18

gem_plugin is installed though. Mongrel 0.3.11. Rails 1.1.

Any idea?

-- 
Jean-Christophe Michel