Cannot Log Back in when Virtualbox VM is Running

[robert1234]

I have noticed that when I am running a virtualbox vm and my monitors turn to sleep mode due to about 30 minutes of inactivity, I can not log back in after I wake them back up. Lightdm displays on one of the monitors and the others show the screen saver. All three are frozen at this point (the cursor is the only thing that responds to my input), and the only way to log back into xfce is to either reboot, or go into a tty and kill lightdm. I am using the nouveau driver. I tested in Debian (using the nouveau driver, all my monitors, and xfce), and when I leave a virtualbox vm on in Debian and let my monitors go into sleep mode. I can log back into xfce just fine, so I suspect it is something with Gentoo. Perhaps a kernel option. Does anyone have any suggestions about what could be wrong? There is no problem when I am not running any virtual machines.