The rubyforge -> ml link seems to be down so here is the link :
http://rubyforge.org/tracker/?func=detail&aid=15425&group_id=426&atid=1698

Let me know if you need any help. I think that it doesn't affect only regexpes.

@knu : don't you think it is related to gc.c:1256 which you introduced
? I am not sure, it's at the limit of my C knowledge..

-- 
Cheers,
  zimbatm