[Boost-users] compiler error on using threads with boost

Hi, I get this compiler error : boost/thread/future.hpp", line 414: Error: Formal argument other of type boost::unique_lock<boost::mutex> in call to boost::unique_lock<boost::mutex>::operator=(boost::unique_lock<boost::mutex>) has an inaccessible copy constructor. Any idea why this is? I'm using the sun compiler to compile it with Regards, iskandar