Server/Console: ext call crashes in rails-server but works in rails-console

Hello,

I use RMagick in Rails 3.0.1 and ruby 1.9.2p0 on OS X 10.6.4

A simple

$ rails c
Loading development environment (Rails 3.0.1)
irb(main):001:0> f = Magick::Image.new(100,100)
=> 100x100 DirectClass 16-bit
irb(main):002:0> quit

works in the rails console but crashes when executed in the rails
server (seg fault).
Any idea what's the difference and why this crashes?

Thanks a lot,
Horst