In the meantime I was able to provoke the exception in a more deterministic manner. Merely incrementing the value of an unsigned int and saving the player profile leads to the exception I mentioned: for (int i=0;i<100;i++) { //this is just a regular size_t variable CURRENT_PROFILE.NextLevel=i; g_GameProgress.SaveToFile(); //this always trows an exception when i==26 g_GameProgress.LoadFromFile(); } The problem does not seem to be related to side-effects in previous file save / reload attempts. If I merely do this, it leads to the same exception: //this is just a regular size_t variable CURRENT_PROFILE.NextLevel=26; g_GameProgress.SaveToFile(); //same exception here! g_GameProgress.LoadFromFile(); the exception is thrown in line 114 basic_binar_iprimitive: if(is.fail()) boost::throw_exception(archive_exception(archive_exception::stream_error)); Thanks for your help, Adrian Grigore