Ran into a bug yesterday, where http://pecl.php.net/uuid in combination with http://pecl.php.net/imagick yielded a segfault when using uuid_create().

After trying to trace it down with a backtrace and cachegrind results, he (and Mikko & Pierre) found that both extensions were built against the libuuid.so.1 file. While that wasn't the issue directly, they did find a work-around that helped the issue - renaming some ini files so uuid was loaded first.