Whenever I'm trying to work something out, the GATEWAY_PROBE_HOST not configured from the advanced options in metasploit always ruins my day. I'm assuming it's a gateway thing (obviously) so I set it from metasploit.com (why is this the default?) to my subnet 192.168.56.0. After that metasploit works relatively fine, however occasionally has very odd issues and overall performance suffers. Last time I tried it crashed, then when I went to kill the process it spit out all the scan results from what I was trying to scan when it crashed straight from the shell prompt. But basically I just want to know what it's for so I can be sure that I set it properly.