Here's my situation. We've got some software that makes use of the boost regex libraries and we've compiled and linked with the ICU libraries enabled. We need this for utf-8 support. Our platforms are Windows (XP and Vista) and OS X. I have a regular expression that is parsing an html page that is utf-8 encoded and it's a rather complex expression, but I've made sure to add anchors such that I don't run into catastrophic backtraking. Another note, I'm using u32regex_search and my flags are match_default | match_partial. I have to use match_partial because the input data is long and I've seen memory exhausted even when I've increased BOOST_REGEX_MAX_BLOCKS (I probably have more work to do on the expression to reduce the complexity). On Windows I have no problems. Partial matches are returned and I eventually get full matches and my code runs great. On OS X, u32regex_search returns and indicates it has found a partial match (what[0].match == false). But what[0].second is set to the end of my input string, so no further matching takes place and my loop ends. This is very different behavior than what I'm seeing on Windows. I know this email is vague, but I can provide any details that would be helpful in solving this issue. Why the difference between Windows and OS X, I've compiled both boost libraries with the same compiler options on both platforms? Is it an ICU compile issue? Thanks, Tommy McClung IMSafer, Inc. Founder tmcclung@imsafer.com