For those using MacPorts, ImageMagick 6.6.5 and Ruby 1.9.2.

If anybody get this error :
/gems/carrierwave-0.5.3/lib/carrierwave/processing/rmagick.rb:248: [BUG] Segmentation fault
ruby 1.9.2p0 (2010-08-18 revision 29036) [x86_64-darwin10.7.0]

Theses are the steps to avoid it (Port).
port uninstall ImageMagick 
port edit ImageMagick
Add --disable-openmp to configure.args (near line 100) 
port install ImageMagick

Uninstall imagemagick:

brew remove imagemagick

Delete the cache:

rm -rf 'brew --cache imagemagick'

Then re-install the package with this flag:

brew install -f imagemagick --disable-openmp