I've installed LM13 in VB several times, all with 3D enabled, It works great, but sometimes moving windows around or scrolling in a Window makes the screen all white, which requires restarting from a console.
But I don't think that's your problem though.
For my VB settings, I've enabled 2 CPU cores(need to enable APIC), 128 mb ram for video, 3D enabled, 1.5GB ram. Been running for 2 days now, am loving it. Only froze with the white screen 4-6 times so far.
Mint 13 Maya 64-bit