[BUG] Bus Error - What causes this in Ruby?

Question

I have run into this error 5 or 10 times over the past few years and have never found a clear answer to this problem. Here is the error:

$ rake db:migrate
/usr/lib/ruby/gems/1.8/gems/libxml-ruby-0.9.5/lib/libxml_ruby.bundle: [BUG] Bus Error
ruby 1.8.7 (2009-06-12 patchlevel 174) [i686-darwin9.7.0]

Abort trap

The app I am running this in is using RMagick.

I have run into this problem when installing ImageMagick a while ago, and when installing Nokogiri, and when installing MySQL. For Nokogiri it was because I needed a more recent version of libxml. What are your thoughts on this? Any fixes? How can I check the version of RMagick the project is loading?

I am on a Mac, 10.5.8.

Thanks for the help, Lance