Many people are having this problem when using rcov and rspec:
http://rspec.lighthouseapp.com/projects/5645/tickets/309-fix-for-rcov-segfault-2
Fortunately a good guy wrote a patch:
http://tomcopeland.blogs.com/juniordeveloper/2008/08/rcov-crashing-w.html
And now we have a rcov gem with that patch:
$ gem sources -a http://gems.github.com (you only have to do this once)
$ sudo gem install mergulhao-rcov
Hope this helps someone.
Sylvestre Mergulhao
http://mergulhao.info