Apparently, the viewer doesn't crash: it just refuses to start.
The relevant lines in the log file are:
Either you are starting the viewer without the --multiple command line option while another viewer is already started, or you got a stale marker file on your system that somehow can't be removed (hard disk write failure ?)...
Search for "SecondLife.exec_marker" file in the same directory as where you found the logs, and remove it (while no viewer is running), then restart the viewer. If you fail to remove that file while no viewer is running, then something is wrong on your system (probably hard disk issue, or some program (virus ?) accessing permanently to that file and thus "locking" it).