WEBrick crash

Hi all,

Using Rails 2.1.1 and Ruby 1.8.6, WEBrick crashes at first request with
the following trace :

/usr/lib/ruby/1.8/webrick/server.rb:162: [BUG] Segmentation fault

My app used to work well, and this error appeared with no obvious
reason.
Does anyone know where it could come from ?

Thanks a lot.