virtualbox.org

Host:
Lenovo Z710 Core i7-4700MQ 16 GB RAM Hybrid Graphics (Intel HD Graphics 4600 / NVIDIA GeForce GT 745M)
Qualcomm Atheros AR8171/8175 PCI-E Gigabit Ethernet Controller, Intel(R) Wireless-N 7260 running Windows 8.1
VirtualBox 4.3.8 r92456
Extensions Pack installed
NAT and Host-Only Networks (DHCP Server disabled)

Guest OS:
Fedora linux version 20.1 64 bit
2 processors
2 GB system ram
128 MB video memory
Guest additions installed

The VM is running as expected. However, if there is no activity the screen saver is activated on host, the VM container doesn't render the guest when host is awaken and all you get is a black window. I did manage to find a temp kludge... close the VM window by clicking the "X" icon in upper left corner (if windows host) will cause VB to ask if you want to save state, shutdown or power off VM. Select the save state option then restart VM. This will render the guest os vm window properly.

Sounds like a 3D acceleration glitch.

Update.

This issue only occurs if VM was switched to full screen or seamless mode and 3D Acceleration is enabled.

I've seen this before with dual graphics laptops. One low and one high to conserve the battery. You can see in the logs where VirtualBox is struggling with the OpenGL drivers. The Intel portion is low graphics and does not support OpenGL and the nVidia side is what is needed to have OpenGL. Some Laptops have a place you can set it to not drop to low graphics mode when certain conditions exist and some don't. The ones that don't you would need to change a setting the hosts bios.

U R DA MAN perryg!

Dual graphics systems with Intel/NVIDIA does have an option for this via the NVIDIA control panel. The control panel allows you to customize how certain 3D applications utilize the graphics adapters. I customized VB to exclusively use NVIDIA and that solved the issue.