Hi, I get Assertion failed timed_lock(::boost::detail::get_system_time_sentinel()), file c:\boost\thread\win32\basic_timed_mutex.hpp, line 64. Code in basic_timed_mutex.hpp: void lock() { BOOST_VERIFY(timed_lock(::boost::detail::get_system_time_sentinel())); //Line 64 } I read in a previous thread that this was a known bug that is fixed in Boost 1.38 but i am using Boost 1.38. Is this another bug or is it not fixed? This only happends sometimes and it happends when i call wait on a condition variable. Here is my code, i have marked where Assertion failed happends. boost::mutex::scoped_lock lock(_mutex); while(_queue.empty()) { _condition.wait(lock); } //Assertion failed happends here. //Another thread is signaling the condition variable when an element is added to the _queue. I am happy with all sorts of helpful comments. Best regards