First, you still have not supplied the latest VM log (VBox.log), you only included the three older logs (.1, .2, .3) - however I'll assume these are equally representative.
I see no sign of a crash in .1 - all I see is the VM taking a long time to get started, manually powered down before it completed.
The .2 log was incomplete. If this shows the crash then it means VBox is crashing without a "Guru Meditation" dialog - or the host is crashing.
The .3 log is again incomplete.
The only issue I have with your configuration is that I would try setting the guest RAM to 4GB.
Also, I see you are assigning 6 CPU cores to the guest. What is the CPU, how many cores does it have?